Fair Value of Financial Instruments (Carrying Amounts and Estimated Fair Values of Financial Instruments) (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Assets:
Equity securities	$ 1,145,040	$ 1,203,788
Arbitrage trading account	832,000	1,123,000
Loans receivable	420,655	405,248
Carrying Value
Assets:
Fixed maturity securities	23,620,804	22,397,865
Equity securities	1,145,040	1,203,788
Arbitrage trading account	831,705	1,122,599
Loans receivable	419,880	405,453
Cash and cash equivalents	1,720,209	1,974,747
Trading account receivables from brokers and clearing organizations	343,796	60,327
Liabilities:
Due to broker	85,188	70,483
Trading account securities sold but not yet purchased	52,407	73,358
Senior notes and other debt	1,832,822	1,831,158
Subordinated debentures	1,009,988	1,009,808
Fair Value
Assets:
Fixed maturity securities	23,622,102	22,399,426
Equity securities	1,145,040	1,203,788
Arbitrage trading account	831,705	1,122,599
Loans receivable	420,655	405,248
Cash and cash equivalents	1,720,209	1,974,747
Trading account receivables from brokers and clearing organizations	343,796	60,327
Liabilities:
Due to broker	85,188	70,483
Trading account securities sold but not yet purchased	52,407	73,358
Senior notes and other debt	1,435,637	1,425,852
Subordinated debentures	$ 772,422	$ 805,864

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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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI), classified as current.

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Fair value of subordinated debt obligations including, but not limited to, subordinated loan, subordinated bond, subordinated debenture or junior debt.

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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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The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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Fair value portion of liabilities pertaining to principal and customer trading transactions, or which may be incurred with the objective of generating a profit from short-term fluctuations in price as part of an entity's market-making, hedging and proprietary trading. Examples include, but are not limited to, short positions in securities, derivatives and commodities.

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Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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