Fair Value of Financial Instruments (Carrying Amounts and Estimated Fair Values of Financial Instruments) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Assets:
Arbitrage trading account	$ 400,809	$ 452,548
Loans receivable	94,613	97,073
Liabilities:
Due to broker	27,116	20,144
Due to broker	27,116	20,144
Carrying Value
Assets:
Fixed maturity securities	14,180,961	13,606,812
Equity securities	480,620	279,006
Arbitrage trading account	400,809	452,548
Loans receivable	91,799	94,813
Cash and cash equivalents	1,023,710	817,602
Trading accounts receivable from brokers and clearing organizations	423,543	347,228
Liabilities:
Trading account securities sold but not yet purchased	36,143	38,120
Senior notes and other debt	1,427,575	1,882,028
Subordinated debentures	1,198,704	907,491
Fair Value
Assets:
Fixed maturity securities	14,194,955	13,619,620
Equity securities	480,620	279,006
Arbitrage trading account	400,809	452,548
Loans receivable	94,613	97,073
Cash and cash equivalents	1,023,710	817,602
Trading accounts receivable from brokers and clearing organizations	423,543	347,228
Liabilities:
Trading account securities sold but not yet purchased	36,143	38,120
Senior notes and other debt	1,582,290	1,968,996
Subordinated debentures	$ 1,274,088	$ 840,002

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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

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-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
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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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-Publisher FASB
-Name Accounting Standards Codification
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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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Due to broker.

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Due To Broker Fair Value

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Marketable Securities, Fair Value Disclosure

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Trading Accounts Receivable From Brokers, Fair Value Disclosure

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