Investments (Details 3) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Amortized cost and fair value of fixed maturity securities
Due in 1 year or less, Available for sale, Cost or amortized cost	$ 217,012
Due after 1 year through 5 years, Available for sale, Cost or amortized cost	1,062,230
Due after 5 years through 10 years, Available for sale, Cost or amortized cost	1,456,485
Due after 10 years through 15 years, Available for sale, Cost or amortized cost	1,020,759
Due after 15 years, Available for sale, Cost or amortized cost	1,001,045
Securities with contractual maturities, Available for sale, Cost or amortized cost	4,757,531
Mortgage-backed and asset-backed securities, Available for sale, Cost or amortized cost	1,185,629
Available-for-sale fixed maturity Securities, Amortized Cost Basis	5,943,160	5,856,432
Due in 1 year or less, Available for sale, Fair value	219,433
Due after 1 year through 5 years, Available for sale, Fair value	1,098,261
Due after 5 years through 10 years, Available for sale, Fair value	1,524,386
Due after 10 years through 15 years, Available for sale, Fair value	1,045,896
Due after 15 years, Available for sale, Fair value	1,010,679
Securities with contractual maturities, Available for sale, Fair value	4,898,655
Mortgage-backed and asset-backed securities, Available for sale, Fair value	1,195,985
Available-for-sale Securities, Debt Securities, Fair value	$ 6,094,640

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Available For Sale Securities Debt Maturities After Fifteen Years Amortized Cost.

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Available For Sale Securities Debt Maturities After Fifteen Years Fair Value.

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Available For Sale Securities Debt Maturities After Ten Through Fifteen Years Amortized Cost.

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Available For Sale Securities With Contractual Maturities Amortized Cost.

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This item represents the cost of debt securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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Amount of available-for-sale debt securities at cost, net of adjustments, maturing in the sixth fiscal year through the tenth fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings (less any cumulative-effect adjustments, as defined) and fair value hedge accounting adjustments.

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Amount of available-for-sale debt securities at cost, net of adjustments, that do not have a single maturity date and which the entity has decided to disclose separately rather than allocating the cost over several maturity groupings. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings (less any cumulative-effect adjustments, as defined) and fair value hedge accounting adjustments.

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This element represents the portion of the balance sheet assertion valued at fair value by the entity 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. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

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