Fair Value of Financial Instruments (Carrying Amounts and Estimated Fair Values of Financial Instruments) (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Assets:
Equity securities	$ 1,502,237	$ 1,358,201
Arbitrage trading account	1,292,382	1,221,103
Carrying Value
Assets:
Fixed maturity securities	25,899,992	25,047,662
Equity securities	1,502,237	1,358,201
Arbitrage trading account	1,292,382	1,221,103
Loans receivable	265,644	418,913
Cash and cash equivalents	2,606,530	2,539,938
Trading account receivables from brokers and clearing organizations	3,139	11,669
Due from broker	0	629
Liabilities:
Due to broker	176,693	0
Trading account securities sold but not yet purchased	6,576	66,285
Senior notes and other debt	1,829,445	1,829,198
Subordinated debentures	1,010,887	1,010,527
Fair Value
Assets:
Fixed maturity securities	25,900,428	25,048,534
Equity securities	1,502,237	1,358,201
Arbitrage trading account	1,292,382	1,221,103
Loans receivable	265,644	419,074
Cash and cash equivalents	2,606,530	2,539,938
Trading account receivables from brokers and clearing organizations	3,139	11,669
Due from broker	0	629
Liabilities:
Due to broker	176,693	0
Trading account securities sold but not yet purchased	6,576	66,285
Senior notes and other debt	1,447,266	1,440,055
Subordinated debentures	$ 713,744	$ 760,400

Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

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