Consolidated Statement of Income (Unaudited) Consolidated Balance Sheet (Unaudited at September 30, 2014) Consolidated Statement of Changes in Shareholders' Equity (Unaudited) Consolidated Statement of Cash Flows (Unaudited) Revenues Premiums Net investment income Other revenues Total revenues Total revenues Claims and expenses Claims and claim adjustment expenses Amortization of deferred acquisition costs General and administrative expenses Reclassification adjustment impacting general and administrative expense on the income statement Interest expense Total claims and expenses Total claims and expenses Income tax expense (benefit) Income tax expense Income tax (expense) benefit Net income Net income Amounts reclassified from accumulated other comprehensive income, net of taxes Net income per share Net income per share, basic Net income per common share, basic Net income per share, diluted Net income per common share, diluted Weighted average number of common shares outstanding Weighted average number of common shares outstanding, basic Weighted average shares outstanding, basic Weighted average number of common shares outstanding, diluted Weighted average shares outstanding, diluted Other-than-temporary impairment, credit losses recognized in net realized investment gains (losses) Impairment charges Other-than-temporary impairment losses recognized in net realized investment gains (losses) Other-than-temporary impairment, credit losses recognized in net realized investment gains (losses) Assets Fixed maturities, available for sale, at fair value Fixed maturities, available for sale, at fair value (amortized cost $61,043 and $62,196) Fixed maturities, at fair value Cash flows from operating activities Equity securities, available for sale, at fair value Equity securities, available for sale, at fair value (cost $609 and $686) Equity securities, at fair value Real estate investments Short-term securities Other investments Total investments Total investments Cash Cash at beginning of year Cash at end of period Investment income accrued Premiums receivable Reinsurance recoverables Ceded unearned premiums Deferred acquisition costs Goodwill Goodwill acquired Other intangible assets Total other intangible assets, net Other assets Total assets Total assets Liabilities Claims and claim adjustment expense reserves Unearned premium reserves Contractholder payables Payables for reinsurance premiums Debt Other liabilities Total liabilities Total liabilities Shareholders' equity Retained earnings Retained earnings, balance, beginning of year Retained earnings, balance, end of period Accumulated other comprehensive income Accumulated other comprehensive income, net of tax, balance, beginning of year Accumulated other comprehensive income, net of tax, balance, end of period Treasury stock, at cost Treasury stock (at cost), balance, beginning of year Treasury stock (at cost), balance, end of period Treasury stock, at cost Treasury stock, at cost (427.6 and 401.5 shares) Total shareholders' equity Total shareholders' equity Total liabilities and shareholders' equity Total liabilities and shareholders' equity Fixed maturities, available for sale, amortized cost Fixed maturities, amortized cost Equity securities, available for sale, cost Equity securities, cost Common stock, shares issued Common stock, shares authorized Common stock, shares outstanding Common shares outstanding, balance, beginning of year Common shares outstanding, balance, end of period Treasury stock, at cost, shares Common stock [Abstract] Common stock Common stock, employee share-based compensation Common stock, compensation amortization under share-based plans and other changes Dividends Dividends Treasury stock (at cost), treasury stock acquired - share repurchase authorization Treasury stock (at cost), treasury stock acquired - share repurchase authorization Treasury stock (at cost), net shares acquired related to employee share-based compensation plans Treasury stock (at cost), net shares acquired related to employee share-based compensation plans Common shares outstanding, treasury stock acquired - share repurchase authorization Common shares outstanding, treasury stock acquired - share repurchase authorization Common shares outstanding, net shares issued under employee share-based compensation plans Deferred federal income tax expense Equity in income (loss) from other investments Equity in income from other investments Change in premiums receivable Change in premiums receivable Change in reinsurance recoverables Change in reinsurance recoverables Change in deferred acquisition costs Change in deferred acquisition costs Change in unearned premium reserves Other operating activities Cash flows from investing activities Proceeds from sales of investments, fixed maturities Proceeds from sales of investments, other investments Purchases of investments, fixed maturities Purchases of investments, fixed maturities Purchases of investments, equity securities Purchases of investments, equity securities Purchases of investments, real estate investments Purchases of investments, real estate investments Purchases of investments, other investments Purchases of investments, other investments Net sales (purchases) of short-term securities Net purchases of short-term securities Net sales (purchases) of short-term securities Securities transactions in course of settlement Other investing activities Other investing activities Cash flows from financing activities Dividends paid to shareholders Dividends paid to shareholders Treasury stock acquired - share repurchase authorization Treasury stock acquired - share repurchase authorization Treasury stock acquired - net employee share-based compensation Treasury stock acquired - net employee share-based compensation Excess tax benefits from share-based payment arrangements Supplemental disclosure of cash flow information Interest paid Segment Information disclosure Segment Information disclosure [Text Block] Investments disclsoure [Text Block] Fair Value Measurements disclosure Fair Value Measurements disclosure [Text Block] Goodwill and Other Intangible Assets disclosure Goodwill and Other Intangible Assets disclosure [Text Block] Earnings per Share disclosure [Text Block] Share-Based Incentive Compensation disclosure Share-Based Incentive Compensation disclosure [Text Block] Pension Plans, Retirement Benefits and Savings Plans disclosure Pension Plans, Retirement Benefits and Savings Plans disclosure [Text Block] Contingencies, Commitments and Guarantees disclosure Contingencies, Commitments and Guarantees disclosure [Text Block] Consolidating Financial Statements of The Travelers Companies, Inc. and Subsidiaries (Unaudited) disclosure Company's revenues and operating income by segment [Table Text Block] Business segment reconciliations of revenue and income, net of tax [Table Text Block] Asset reconciliation [Table Text Block] Cost and fair value of investments in equity securities [Table Text Block] Securities continuously in an unrealized loss position of greater than 20% of amortized cost by length of time [Table Text Block] Tabular disclosure of gross unrealized investment loss for securities with fair values less than 80% of amortized loss, by length of time in an unrealized loss position of greater than 20% of amortized cost. Impairment charges included in net realized investment gains (losses) [Table Text Block] Cumulative amount of and the changes during the reporting period in the credit losses of other-than-temporary impairments (OTTI) on fixed maturities recognized in the consolidated statement of income for which a portion of the OTTI was recognized in other comprehensive income [Table Text Block] Changes in the Level 3 fair value category [Table Text Block] Goodwill by segment [Table Text Block] Other intangible assets by major asset class [Table Text Block] Tabular disclosure of intangible assets, both finite-lived and indefinite-lived, excluding goodwill. Major asset class detail provided for finite-lived intangible assets only. Earnings per Share disclosure Schedule of segment reporting information, by segment [Table] Segment [Axis] Reportable Segments [Domain] Workers' compensation [Member] Commercial multi-peril [Member] Fidelity and surety [Member] International [Member] Automobile [Member] Homeowners and other [Member] Personal Insurance [Member] Segment reporting information [Line Items] Segment reporting information Net realized investment gains (losses), net of tax Assets by Segment Asset by segment [Line Items] Assets by segment Assets by segment [Table] Investment details [Table] U.S. Treasury securities and obligations of U.S. government and government agencies and authorities [Member] Obligations of states, municipalities and political subdivisions, pre-refunded [Member] Obligations of states, municipalities and political subdivisions, all other (not pre-refunded) [Member] Obligations of states, municipalities and political subdivisions [Member] Debt securities issued by foreign governments [Member] All other corporate bonds [Member] Redeemable preferred stock [Member] Fixed maturities [Member] Equity securities, public common stock [Member] Equity securities, non-redeemable preferred stock [Member] Equity securities [Member] Investment disclosure details [Line Items] Investment disclosure details Continuous unrealized loss position less than 12 months, fair value Continuous unrealized loss position 12 months or longer, fair value Available-for-sale securities for which fair value is less than 80% of amortized cost, greater than 12 months Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position of greater than 20% of amortized cost for greater than twelve months. Available-for-sale securities for which fair value is less than 80% of amortized cost, total Available-for-sale securities for which fair value is less than 80% of amortized cost, total Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale in a continuous loss position of greater than 20% of amortized cost. Cumulative amount of and the changes during the reporting period in the credit losses of other-than-temporary impairments (OTTI) on fixed maturities recognized in the consolidated statement of income for which a portion of the OTTI was recognized in other comprehensive income [Table] Debt Security [Axis] Cumulative amount of and the changes during the reporting period in the credit losses of other-than-temporary impairments (OTTI) on fixed maturities recognized in the consolidated statement of income for which a portion of the OTTI was recognized in other comprehensive income [Axis] Fixed maturities [Domain] Cumulative amount of and the changes during the reporting period in the credit losses of other-than-temporary impairments (OTTI) on fixed maturities recognized in the consolidated statement of income for which a portion of the OTTI was recognized in other comprehensive income [Roll Forward] Cumulative amount of and the changes during the reporting period in the credit losses of other-than-temporary impairments (OTTI) on fixed maturities recognized in the consolidated statement of income for which a portion of the OTTI was recognized in other comprehensive income [Line Items] Cumulative amount of and the changes during the reporting period in the credit losses of other-than-temporary impairments (OTTI) on fixed maturities recognized in the consolidated statement of income for which a portion of the OTTI was recognized in other comprehensive income Cumulative OTTI credit losses recognized for securities held Cumulative OTTI credit losses recognized for securities held, beginning of period Cumulative OTTI credit losses recognized for securities still held, end of period Additions for OTTI securities where no credit losses were previously recognized Reductions due to sales/defaults of credit-impaired securities Reductions due to sales/defaults of credit-impaired securities Additions for OTTI securities where credit losses have been previously recognized Percent of fixed maturities for which a pricing service estimates fair value Convertible bonds held containing embedded conversion options that are valued separately from the host bond contract and disclosed in Level 2 Level within the fair value hierarchy at which the Company's financial assets are measured [Table] Level within the fair value hierarchy at which the Company's financial assets are measured [Axis] Level within the fair value hierarchy at which the Company's financial assets and financial liabilites are measured [Axis] Level within the fair value hierarchy at which the Company's financial assets are measured [Domain] Level 1 [Member] Level 2 [Member] Level 3 [Member] Level within the fair value hierarchy at which the Company's financial assets are measured [Line Items] Level within the fair value hierarchy at which the Company's financial assets are measured Total invested assets measured on a recurring basis Changes in Level 3 fair value category [Table] Changes in Level 3 fair value category [Line Items] Changes in Level 3 fair value category Changes in Level 3 fair value category [Roll Forward] Level 3 fair value category, balance Level 3 fair value category, beginning balance Level 3 fair value category, ending balance Level 3 fair value category purchases Level 3 fair value category sales Level 3 fair value category sales Level 3 fair value category settlements/maturities Level 3 fair value category settlements/maturities Gross transfers into Level 3 Gross transfers out of Level 3 Gross transfers out of Level 3 Intangible assets not subject to amortization Goodwill by segment [Table] Goodwill [Line Items] Goodwill by segment Other intangible assets by major asset class [Axis] Other intangible assets subject to amortization [Domain] Other intangible assets by major asset class [Line Items] Other intangible assets by major asset class Intangible assets subject to amortization, gross carrying amount Intangible assets subject to amortization, accumulated amortization Total other intangible assets, accumulated amortization Intangible assets subject to amortization, net Intangible assets subject to amortization, net Net income available to common shareholders -- basic Net income available to common shareholders -- basic Net income available to common shareholders -- diluted Net income available to common shareholders -- diluted Weighted average effects of dilutive securities, stock options and performance shares (in shares) Stock options exercisable at end of period, number (in shares) Stock options exercisable at end of period, weighted average exercise price (per share) Stock options exercisable at end of period, aggregate intrinsic value Total compensation cost recognized in earnings for all share-based incentive compensation awards Tax benefits recognized in earnings related to compensation costs Total unrecognized compensation cost related to all nonvested share-based incentive compensation awards Unfunded commitments to private equity limited partnerships and real estate partnerships Schedule of guarantor obligations [Table] Guarantor obligations by nature [Axis] Guarantor obligations, nature [Domain] Indemnifications related to the sale of businesses [Member] Guarantor obligations [Line Items] Guarantor obligations Maximum amount of contingent obligation Amount indemnified by a third party Amount recognized on balance sheet for contingent obligation Amount of certain debt obligations of TPC that are unconditionally guaranteed by The Travelers Companies, Inc. Consolidating Financial Statements Legal entity [Axis] Entity [Domain] Other Subsidiaries [Member] Travelers [Member] Eliminations [Member] Additional paid-in capital Net adjustments to reconcile net income to net cash provided by operating activities Dividends paid to parent company Registrant name Central index key Document type Document period end date Amendment flag After-tax interest expense Payment of debt Payment of debt Income before income taxes Income before income taxes Total reclassifications Retained earnings [Abstract] Retained earnings Adjustments to reconcile net income to net cash provided by operating activities: Guarantees disclosure Operating income (loss) Operating income Guarantees of certain investments and third-party loans [Member] Guarantees of certain insurance policy obligations [Member] Net cash provided by operating activities Net cash provided by operating activities Net cash provided by (used in) investing activities Net cash used in investing activities Net cash used in financing activities Net cash used in financing activities Amortization expense for other intangible assets Income taxes paid Income taxes paid (received) Unrealized investment losses [Table Text Block] Level within the fair value hierarchy at which the Company's financial assets and financial liabilities reported at fair value are measured [Table Text Block] Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member] Contingencies and Commitments disclosure Investments in various publicly-traded securities, including mutual funds and other small holdings disclosed in Level 1 [Member] Investments in various publicly-traded securities including mutual funds and other small holdings, disclosed within other investments. Accumulated other comprehensive income, net of tax Contractholder receivables Fee income Consolidated Statement of Comprehensive Income (Unaudited) Other comprehensive income (loss): Changes in net unrealized gains on investment securities having no credit losses recognized in the consolidated statement of income Net changes in benefit plan assets and obligations Net changes in benefit plan assets and obligations Other comprehensive income (loss) before income taxes Other comprehensive income (loss) before income taxes Income tax expense (benefit), other comprehensive income (loss) Income tax expense (benefit) Other comprehensive income (loss), net of taxes Other comprehensive income (loss), net of taxes Other comprehensive income (loss) Comprehensive income (loss) Comprehensive income Deferred tax liability Deferred taxes Common stock (1,750.0 shares authorized; 331.4 and 353.5 shares issued and outstanding) Common stock, balance, beginning of year Common stock, balance, end of period Common stock Common Share Repurchases disclosure Treasury stock (at cost) Common shares outstanding Net increase (decrease) in cash Net increase (decrease) in cash Investments disclosure Accounting Policies, Basis of Presentation [Policy Text Block] Accounting Policies, Adoption of Accounting Standards Updates [Policy Text Block] Number of reportable business segments Continuous unrealized loss position, total, fair value Continuous unrealized loss position, total, fair value Other investments [Member] Carrying value and fair value of financial instruments disclosed, but not carried, at fair value and the level within the fair value hierarchy at which such financial instruments are measured on a recurring basis [Table Text Block] Fair value of the fixed maturities for which the Company used an internal pricing matrix Fair value of the fixed maturities for which the Company received a broker quote Percent of debt, including commercial paper, for which a pricing service estimates fair value Percent of short-term securities for which a pricing service estimates fair value Level 3 fair value category, total realized and unrealized investment gains (losses) reported in net realized investment gains (losses) Level 3 fair value category, total unrealized investment gains (losses) reported in increases (decreases) in other comprehensive income Carrying value and fair value of the financial assets and financial liabilities disclosed, but not carried, at fair value and the level within the fair value hierarchy at which such assets and liabilities are measured on a recurring basis [Table] Financial assets and financial liabilities measured on a recurring basis [Axis] Fair Value [Member] Carrying Value [Member] Financial Instruments [Line Items] Financial Instruments Debt, fair value disclosure Debt Commercial paper Estimated intangible asset amortization expense, 2015 Estimated intangible asset amortization expense, 2016 Estimated intangible asset amortization expense, 2017 Estimated intangible asset amortization expense, 2018 Other intangible assets by major asset class Other intangible assets by major asset class [Table] Treasury Stock [Table] Share Repurchase Program [Axis] Share Repurchase Program [Domain] Board of Directors Approved Repurchase Authorizations [Member] Repurchase activity [Line Items] Repurchase activity Number of shares repurchased (in shares) Cost of shares repurchased Average cost per share repurchased Earnings per share reconciliation [Table Text Block] Changes in net unrealized gains on investment securities having credit losses recognized in the consolidated statement of income Consolidating Financial Statements of The Travelers Companies, Inc. and Subsidiaries (Unaudited) disclosure [Text Block] Consolidating Statement of Income (Unaudited) [Table Text Block] Consolidating Balance Sheet (Unaudited) [Table Text Block] Consolidating Statement of Cash Flows (Unaudited) [Table Text Block] TPC [Member] Stock options exercisable at end of period, weighted average contractual life remaining Weighted-average period of recognition for unrecognized compensation cost (in years) Other Comprehensive Income and Accumulated Other Comprehensive Income disclosure Other Comprehensive Income and Accumulated Other Comprehensive Income disclosure [Text Block] Changes in accumulated other comprehensive income (AOCI) [Table Text Block] Pretax components of other comprehensive income (loss) and the related income tax expense (benefit) for each component [Table Text Block] Equity Components [Axis] Total Accumulated Other Comprehensive Income [Domain] Total Other Comprehensive Income [Domain] Changes in Net Unrealized Gains on Investment Securities Having No Credit Losses Recognized in the Consolidated Statement of Income [Member] Changes in Net Unrealized Gains on Investment Securities Having Credit Losses Recognized in the Consolidated Statement of Income [Member] Net Benefit Plan Assets and Obligations Recognized in Shareholders' Equity [Member] Other comprehensive income (loss), net of taxes, before other comprehensive income (loss) of subsidiaries Other comprehensive income (loss), net of taxes, before other comprehensive income (loss) of subsidiaries Other comprehensive income (loss) of subsidiaries Net changes in unrealized foreign currency translation Basis of Presentation and Accounting Policies disclosure Basis of Presentation and Accounting Policies disclosure [Text Block] Information for fully vested stock option awards [Table Text Block] Summary of the components of net periodic benefit cost for the Company's pension and postretirement benefit plans recognized in the consolidated statement of income [Table Text Block] Proceeds from sales of investments, equity securities Estimated intangible asset amortization expense, remainder of 2014 Issuance of common stock - employee share options Benefit Plans [Axis] Pension and postretirement benefit plans [Domain] Pension Plans [Member] Postretirement Benefit Plans [Member] Defined benefit plan disclosure [Line Items] Defined benefit plan disclosure Service cost Interest cost on benefit obligation Expected return on plan assets Expected return on plan assets Amortization of unrecognized net actuarial (gain) loss Amortization of unrecognized net actuarial (gain) loss Net periodic benefit cost Net periodic benefit cost Net Unrealized Foreign Currency Translation [Member] Unrealized investment losses for securities for which fair value is less than 80% of amortized cost, as a percentage of the combined fixed maturity and equity security portfolios on a pretax basis Unrealized investment loss in accumulated other comprehensive income, before tax, on investments in debt and equity securities classified as available-for-sale and with fair value less than 80% of amortized cost, as a percentage of the aggregate value of available-for-sale securities. Unrealized investment losses for securities for which fair value is less than 80% of amortized cost, as a percentage of shareholders' equity on an after-tax basis Unrealized investment loss in accumulated other comprehensive income, net of tax, on investments in debt and equity securities classified as available-for-sale and with fair value less than 80% of amortized cost, as a percentage of shareholders' equity. Derivatives [Table] Derivative by Nature [Axis] Derivative, Name [Domain] Futures [Member] Derivative Instrument [Axis] Derivative Contract [Domain] U.S. Treasury notes contracts [Member] Derivative [Line Items] Derivative Available-for-sale securities for which fair value is less than 80% of amortized cost, 3 months or less Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position of greater than 20% of amortized cost for less than three months. Consolidation Items [Axis] Consolidation Items [Domain] Reportable Segments [Member] Interest Expense & Other [Member] Other [Member] Products and Services [Axis] Products and Services [Domain] Commercial Property [Member] Other [Member] Total operating revenues Total operating revenues Amortized cost and fair value of investments in fixed maturities [Table Text Block] Investment type [Axis] Net realized investment gains (losses) Net realized investment gains Net realized investment gain (loss) Net realized investment gains Reclassification adjustment impacting net realized investment gains on the income statement Total other intangible assets, gross carrying amount Total other intangible assets, gross carrying amount Customer-related [Member] Pretax components of the amounts reclassified from accumulated other comprehensive income and the related income tax expense (benefit) for each component [Table Text Block] Accumulated Other Comprehensive Income [Table] Accumulated other comprehensive income (loss) [Line Items] Accumulated other comprehensive income (loss) Other comprehensive income before reclassifications Amounts reclassified from accumulated other comprehensive income Amounts reclassified from accumulated other comprehensive income Reclassifications out of accumulated other comprehensive income [Table] Reclassification out of Accumulated Other Comprehensive Income [Axis] Reclassification out of Accumulated Other Comprehensive Income [Domain] Reclassification out of Accumulated Other Comprehensive Income [Member] Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] Reclassification Adjustment out of Accumulated Other Comprehensive Income Proceeds from maturities of fixed maturities Effect of exchange rate changes on cash Consolidating Statement of Income [Table] Consolidating Statement of Income [Line Items] Consolidating Statement of Income Net income of subsidiaries Consolidating Balance Sheet [Table] Consolidating Balance Sheet [Line Items] Consolidating Balance Sheet Consolidating Statement of Cash Flows [Table] Consolidating Statement of Cash Flows [Line Items] Consolidating Statement of Cash Flows Capital contributions Proceeds from sales of investments, real estate investments General Liability [Member] Disclosure Items [Domain] Total investments [Domain] Deferred taxes Range [Axis] Range [Domain] Maxiumum [Member] Transfers from Level 1 to Level 2 Transfers from Level 2 to Level 1 Loss Contingencies [Table] Litigation Case [Axis] Asbestos Direct Action Litigation [Domain] Statutory and Hawaii Actions [Member] Common Law Claims [Member] Loss Contingencies [Line Items] Loss Contingencies Number of purported class action suits filed against TPC and other insurers in state court in West Virginia relative to asbestos direct action litigation Settlement amount Settlement amount Number of remaining objectors to which the notice of the 1986 Orders was deemed insufficient to bar contribution claims against TPC Gain Contingencies [Table] Gain Contingency, Nature [Axis] Gain Contingency, Nature [Domain] United States Fidelity & Guaranty Company v. American Re-Insurance Company, et al. [Member] Gain Contingencies [Line Items] Gain Contingencies Number of other reinsurers beside American Re against which judgment was entered in a reinsurance dispute Interest related to settlement award Interest related to settlement award Number of discrete issues modified in part by the summary judgment in reinsurance dispute Depreciation and amortization Change in claims and claim adjustment expense reserves Change in claims and claim adjustment expense reserves Amortization expense for other intangible assets by major asset class [Table Text Block] Reportable Legal Entities [Member] Available-for-sale securities for which fair value is less than 80% of amortized cost, greater than 3 months, 6 months or less Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position of greater than 20% of amortized cost for greater than three months through six months. Total other-than-temporary impairment gains (losses) Before considering whether or not such amounts are recognized in earnings or other comprehensive income, the total of (1) the amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary and (2) the amount by which the fair value of an investment is more than the amortized cost basis for available-for-sale securities that have had a previous credit impairment. Total other-than-temporary impairment gains (losses) Unrealized gains from other changes in total other-than-temporary impairments recognized in other comprehensive income (loss) as part of changes in net unrealized gains on investment securities having credit losses recognized in the consolidated statement of income Other-than-temporary impairment gains recognized in other comprehensive income Amount before tax of other than temporary impairment (OTTI) loss or recovery on investments in available-for-sale securities, recognized in other comprehensive loss. Common Share Repurchases disclosure [Text Block] Other fixed maturities [Member] Debt instruments issued by corporations, governments and governmental agencies, municipalities, and other institutions. Excludes securities collateralized by residential real estate mortgage loans. Available-for-sale securities for which fair value is less than 80% of amortized cost, greater than 6 months, 12 months or less Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position of greater than 20% of amortized cost for greater than six months through twelve months. Investments [Table] Impairment charges [Line Items] Impairment charges Investment in non-public common and preferred equity securities where the fair value estimate is determined either internally or by an external fund manager and therefore disclosed in Level 3 [Member] Investments in various non-public common and preferred equity securities, disclosed within other investments. Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Recurring basis [Member] Fair value adjustment on claims and claim adjustment expense reserves, reinsurance recoverables and other contract-related intangibles [Member] Stock options vested at end of period, number (in shares) As of the balance sheet date, the number of shares into which fully vested stock options outstanding can be converted under the option plan. Stock options vested at end of period, weighted average exercise price (per share) As of the balance sheet date, the weighted-average exercise price for outstanding stock options that are fully vested. Stock options vested at end of period, weighted average contractual life remaining Weighted average remaining contractual term for fully vested options outstanding. Stock options vested at end of period, aggregate intrinsic value Amount of difference between fair value of the underlying shares reserved for issuance and exercise prices of fully vested options outstanding. Benefit Plans [Table] Number of reinsurers with whom the Company has reached a settlement agreeement Investment in subsidiaries Acquisition, net of cash acquired Acquisition, net of cash acquired Percent of common stock owned Retained earnings, other Net periodic benefit cost, amortization of unrecognized prior service benefit Business Acquisition [Table] Business Acquisition [Axis] Business Acquisition Acquiree [Domain] Dominion [Member] Business Acquisition [Line Items] Business Acquisition Purchase price Assets acquired Liabilities assumed Intangible assets acquired Gross unrealized gains, fixed maturities Gross unrealized gains Gross unrealized losses, fixed maturities Gross unrealized losses Gross unrealized gains, equity securities Gross unrealized gains Gross unrealized losses, equity securities Gross unrealized losses Continuous unrealized loss position less than 12 months, gross unrealized losses Continuous unrealized loss position 12 months or longer, gross unrealized losses Continuous unrealized loss position, total, gross unrealized losses Continuous unrealized loss position, total, gross unrealized losses Accumulated other comprehensive income [Roll Forward] Remaining capacity under share repurchase authorization Participating share-based awards - allocated income Participating share-based awards - allocated income Consolidating Statement of Comprehensive Income (Unaudited) [Table Text Block] Consolidating Statement of Comprehensive Income [Table] Consolidating Statement of Comprehensive Income [Line Items] Consolidating Statement of Comprehensive Income Notional value of open contracts Number of shares initially available for issuance under the 2014 Incentive Plan Adjustments to book value of credit-impaired securities due to changes in cash flows Adjustments to book value of credit-impaired securities due to changes in cash flows Business and International Insurance [Member] Number of reportable business segments impacted by announced realignment Bond & Specialty Insurance [Member] Geographical [Axis] Geographical [Domain] U.S. [Member] Domestic [Member] Amendment description Current fiscal year end date Well-known seasoned issuer Voluntary filers Current reporting status Filer category Common stock shares outstanding Document fiscal year focus Document fiscal period focus Issuance of debt Schedule of Equity Method Investments [Table] Investment, Name [Axis] Investment, Name [Domain] JMalucelli - Brazilian joint venture [Member] Equity method investment [Line Items} Equity method investment Total settlement amount Total settlement amount Total settlement amount Annual interest rate accruing on judgment not yet paid Asbestos Direct Action Litigation [Member]