Fair Value Measurements - Financial instruments not carried at fair value (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Fixed maturities, held to maturity	$ 0us-gaap_HeldToMaturitySecurities	$ 2,858,695us-gaap_HeldToMaturitySecurities
Deposit Liabilities	1,245,367us-gaap_DepositContractsLiabilities	1,509,243us-gaap_DepositContractsLiabilities
Notes payable and debt	1,662,580us-gaap_LongTermDebt	2,263,203us-gaap_LongTermDebt
Carrying Value
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Fixed maturities, held to maturity	0	2,858,695
Other investments - structured transactions	354,382	294,048
Financial Assets	354,382	3,152,743
Deposit Liabilities	1,245,367	1,509,243
Notes payable and debt	1,662,580	2,263,203
Financial Liabilities	2,907,947	3,772,446
Fair Value
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Fixed maturities, held to maturity	0	3,131,235
Other investments - structured transactions	371,625	296,799
Financial Assets	371,625	3,428,034
Deposit Liabilities	1,543,761	1,718,394
Notes payable and debt	1,897,854	2,429,412
Financial Liabilities	$ 3,441,615	$ 4,147,806

Carrying amount of liabilities as of the balance sheet date pertaining to amounts received by the insurer or reinsurer from the insured (including a ceding company) under insurance or reinsurance contracts for which insurance risk is not transferred.

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Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Aggregate value of financial instrument assets that are not carried at fair value in the financial statements.

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Aggregate value of financial instrument liabilities that are not carried at fair value in the financial statements.

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The Other investments balance disclosed within the Fair Value Measurements tables exclude certain structured transactions including certain investments in project finance transactions, a payment obligation and liquidity financing provided to a structured credit vehicle as a part of a third party medium term note facility.

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