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Fair Value of Financial Instruments (Carrying Amounts and Estimated Fair Values of Financial Instruments) (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Assets:
Equity securities	$ 1,078,092	$ 1,090,347
Arbitrage trading account	1,222,000	938,000
Carrying Value
Assets:
Fixed maturity securities	21,082,676	20,178,308
Equity securities	1,078,092	1,090,347
Arbitrage trading account	1,221,861	938,049
Loans receivable	349,325	201,271
Cash and cash equivalents	1,580,270	1,363,195
Trading account receivables from brokers and clearing organizations	40,705	303,614
Due from broker	0	36,747
Liabilities:
Due to broker	128,563	0
Trading account securities sold but not yet purchased	81,273	9,357
Senior notes and other debt	1,828,422	1,827,951
Subordinated debentures	1,009,449	1,009,090
Fair Value
Assets:
Fixed maturity securities	21,084,502	20,181,547
Equity securities	1,078,092	1,090,347
Arbitrage trading account	1,221,861	938,049
Loans receivable	349,310	198,244
Cash and cash equivalents	1,580,270	1,363,195
Trading account receivables from brokers and clearing organizations	40,705	303,614
Due from broker	0	36,747
Liabilities:
Due to broker	128,563	0
Trading account securities sold but not yet purchased	81,273	9,357
Senior notes and other debt	1,422,506	1,480,076
Subordinated debentures	$ 825,344	$ 929,598

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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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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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