Statement of Financial Position [Abstract] Current assets Current assets [Abstract] Cash and cash equivalents Short-term investments Receivables Receivables [Abstract] Energy marketing Gas, unbilled and other Less allowance for uncollectible accounts Total receivables, net Inventories, net Assets held for sale Regulatory assets Derivative instruments Other Total current assets Long-term assets and other deferred debits Long-term assets and other deferred debits [Abstract] Property, plant and equipment Less accumulated depreciation Property, plant and equipment, net Goodwill Regulatory assets Intangible assets Derivative instruments Other Total long-term assets and other deferred debits Total assets Current liabilities Current liabilities [Abstract] Energy marketing trade payables Short-term debt Other accounts payable - trade Accrued expenses Current portion of long-term debt Regulatory liabilities Temporary LIFO liquidation Customer deposits and credit balances Accrued environmental remediation liabilities Derivative instruments Liabilities held for sale Other Total current liabilities Long-term liabilities and other deferred credits Long-term liabilities and other deferred credits [Abstract] Long-term debt Accumulated deferred income taxes Regulatory liabilities Accrued pension and retiree welfare benefits Accrued environmental remediation liabilities Derivative instruments Other Total long-term liabilities and other deferred credits Total liabilities and other deferred credits Equity Equity [Abstract] Common stock, $5 par value; 750,000,000 shares authorized: outstanding: 119,464,063 shares at June 30, 2014, 118,888,876 shares at December 31, 2013 and 118,560,687 shares at June 30, 2013 Additional paid-in capital Retained earnings Accumulated other comprehensive loss Treasury shares, at cost: 216,523 shares at June 30, 2014 and December 31, 2013 and June 30, 2013 Total common shareholders’ equity Noncontrolling interest Total equity Total liabilities and equity Common stock, par value (in Dollars per share) Common stock, shares authorized Common stock, shares outstanding Treasury shares, shares Income Statement [Abstract] Operating revenues (includes revenue taxes of $26 and $94 for the three and six months in 2014 and $24 and $74 for the three and six months in 2013) Operating expenses Operating expenses [Abstract] Cost of goods sold Operation and maintenance Depreciation and amortization Taxes other than income taxes Total operating expenses Gain on disposition of assets Operating income Other income Interest expense, net Income before income taxes Income tax expense Income from continuing operations Income (loss) from discontinued operations, net of tax Net income Less net income attributable to the noncontrolling interest Net income attributable to AGL Resources Inc. Per common share information Per common share information [Abstract] Basic earnings (loss) per common share Basic earnings (loss) per common share [Abstract] Continuing operations (in Dollars per share) Discontinued operations (in Dollars per share) Basic earnings per common share attributable to AGL Resources Inc. common shareholders (in Dollars per share) Diluted earnings (loss) per common share Diluted earnings (loss) per common share [Abstract] Continuing operations (in Dollars per share) Discontinued operations (in Dollars per share) Diluted earnings per common share attributable to AGL Resources Inc. common shareholders (in Dollars per share) Cash dividends declared per common share (in Dollars per share) Weighted average number of common shares outstanding Weighted average number of common shares outstanding [Abstract] Basic (in Shares) Diluted (in Shares) Operating revenues, revenue taxes Statement of Comprehensive Income [Abstract] Net income Less income (loss) from discontinued operations, net of tax Income from continuing operations Other comprehensive income (loss), net of tax Other comprehensive income (loss), net of tax [Abstract] Retirement benefit plans Retirement benefit plans [Abstract] Reclassification of actuarial losses to net benefit cost (net of income tax of $2 and $3 for the three and six months ended June 30, 2014, and $3 and $5 for the three and six months ended June 30, 2013) Reclassification of prior service credits to net benefit cost (net of income tax of $(1) for the six months ended June 30, 2013) Retirement benefit plans Cash flow hedges, net of tax Cash flow hedges, net of tax [Abstract] Net derivative instrument (losses) gains arising during the period (net of income tax of $1 for the three months ended June 30, 2013) Reclassification of realized derivative instrument (gains) losses to net income (net of income tax of $(1) for the three and six months ended June 30, 2014 and $1 for the six months ended June 30, 2013) Cash flow hedges, net Other comprehensive income, net of tax Comprehensive income Less comprehensive income attributable to noncontrolling interest Comprehensive income from continuing operations attributable to AGL Resources Inc. Reclassification of losses to net benefit cost, income tax Reclassification of prior service credits to net benefit cost, income tax Net derivative instrument gains (losses) arising during the period, income tax Reclassification of realized derivative losses to net income, income tax Statement of Stockholders' Equity [Abstract] Equity Component [Domain] Balance Balance (in Shares) Other comprehensive income Dividends on common stock Distributions to noncontrolling interest Stock granted, share-based compensation, net of forfeitures Stock issued, dividend reinvestment plan Stock issued, dividend reinvestment plan (in Shares) Stock issued, share-based compensation, net of forfeitures Stock issued, share-based compensation, net of forfeitures (in Shares) Stock-based compensation expense, net of tax Balance Balance (in Shares) Dividends on common stock, per share Statement of Cash Flows [Abstract] Cash flows from operating activities Cash flows from operating activities [Abstract] Adjustments to reconcile net income to net cash flow provided by operating activities Adjustments to reconcile net income to net cash flow provided by operating activities [Abstract] Loss from discontinued operations, net of taxes Deferred income taxes Change in derivative instrument assets and liabilities Gain on disposition of assets Changes in certain assets and liabilities Changes in certain assets and liabilities [Abstract] Inventories, net of temporary LIFO liquidation Receivables, other than energy marketing Energy marketing receivables and trade payables, net Accrued expenses Prepaid taxes Trade payables, other than energy marketing Deferred/accrued natural gas costs Other, net Net cash flow provided by operating activities for discontinued operations Net cash flow provided by operating activities Cash flows from investing activities Cash flows from investing activities [Abstract] Expenditures for property, plant and equipment Net decrease in short-term investments Acquisitions of assets Disposition of assets Other Net cash flow used in investing activities for discontinued operations Net cash flow used in investing activities Cash flows from financing activities Cash flows from financing activities [Abstract] Net repayments of commercial paper Dividends paid on common shares Distribution to noncontrolling interest Payment of senior notes Issuance of senior notes Other, net Net cash flow used in financing activities Net increase in cash and cash equivalents - continuing operations Net (decrease) increase in cash and cash equivalents - discontinued operations Cash and cash equivalents (including held for sale) at beginning of period Cash and cash equivalents (including held for sale) at end of period Less cash and cash equivalents held for sale at end of period Cash and cash equivalents (excluding held for sale) at end of period Cash paid during the period for Cash paid during the period for [Abstract] Interest Income taxes Non cash financing transaction Non cash financing transaction [Abstract] Refinancing of gas facility revenue bonds Disclosure Text Block [Abstract] Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Accounting Policies [Abstract] Significant Accounting Policies [Text Block] Regulatory Assets and Liabilities Disclosure [Abstract] Schedule of Regulatory Assets and Liabilities [Text Block] Fair Value Disclosures [Abstract] Fair Value Disclosures [Text Block] Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative Instruments and Hedging Activities Disclosure [Text Block] Compensation and Retirement Disclosure [Abstract] Pension and Other Postretirement Benefits Disclosure [Text Block] Debt Disclosure [Abstract]