Fair Value of Financial Instruments (Carrying Amounts and Estimated Fair Values of Financial Instruments) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Assets:
Equity securities	$ 972,629us-gaap_TradingSecurities	$ 450,648us-gaap_TradingSecurities
Loans receivable	283,836	325,219
Payables to Broker-Dealers and Clearing Organizations	165,420	0
Fair Value
Assets:
Fixed maturity securities	12,673,353	12,725,806
Equity securities available for sale	174,709	170,991
Equity securities	972,629	450,648
Loans receivable	283,836	325,219
Cash and cash equivalents	614,695	674,441
Trading account receivables from brokers and clearing organizations	0	371,034
Liabilities:
Trading account securities sold but not yet purchased	99,299	106,079
Subordinated debentures	354,480	332,640
Senior notes and other debt	2,388,949	2,344,292
Carrying Value
Assets:
Fixed maturity securities	12,652,269	12,705,160
Equity securities available for sale	174,709	170,991
Equity securities	972,629	450,648
Loans receivable	280,769	322,012
Cash and cash equivalents	614,695	674,441
Trading account receivables from brokers and clearing organizations	0	371,034
Due from broker fair value	18,260	23,133
Payables to Broker-Dealers and Clearing Organizations	165,420	0
Liabilities:
Trading account securities sold but not yet purchased	99,299	106,079
Subordinated debentures	340,125	340,060
Senior notes and other debt	$ 2,112,456	$ 2,115,527

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

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-Publisher FASB

-Name Accounting Standards Codification

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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

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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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Amount payable to broker-dealers and clearing organizations, including, but not limited to, securities failed-to-receive, certain deposits received for securities loaned, open transactions, and floor-brokerage payables.

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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 investments in debt and equity securities and other forms of securities that provide ownership interests classified as trading.

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Due from 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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