Derivative Instruments - Narrative (Details) - USD ($) $ in Thousands		3 Months Ended				6 Months Ended
		Jun. 30, 2015		Jun. 30, 2014		Jun. 30, 2015		Jun. 30, 2014		Dec. 31, 2014
Derivative [Line Items]
Cumulative net realized and unrealized loss on life retrocession embedded derivative		$ (381,300)				$ (381,300)
Gross amounts recognized in balance sheet		228,475				228,475				$ 136,659
Net realized and unrealized gains (losses) on derivative instruments		48,509		$ 11,599		65,030		$ 13,409
Gross amounts not offset in the balance sheet - cash collateral		132,050				132,050				78,580
Net results from structured products		5,257	[1]	34,885	[2]	10,282	[3]	42,838	[4]
Fair value hedges | Deposit liabilities
Derivative [Line Items]
Remaining balance		134,054		$ 142,580		134,054		$ 142,580
Structured indemnity | Fair value hedges | Deposit liabilities
Derivative [Line Items]
Remaining balance		47,000				47,000
Structured indemnity | Interest expense
Derivative [Line Items]
Net results from structured products		28,700
Derivatives not designated as hedging instruments
Derivative [Line Items]
Asset derivative notional amount		599,833				599,833				592,791
Gross amounts recognized in balance sheet	[5]	18,800				18,800				14,797
Other non-investment derivatives | Derivatives not designated as hedging instruments | Other credit derivatives
Derivative [Line Items]
Asset derivative notional amount		30,281				30,281				31,060
Gross amounts recognized in balance sheet		71				$ 71				$ 60
Net realized and unrealized gains (losses) on derivative instruments		$ 100

[1] The net results from P&C structured products include net investment income and interest expense of $16.0 million and $10.6 million, respectively.

[2] The net results from P&C structured products include net investment income and interest credit of $16.9 million and $18.2 million, respectively.

[3] The net results from P&C structured products include net investment income and interest expense of $31.1 million and $20.6 million, respectively.

[4] The net results from P&C structured products include net investment income and interest credit of $35.7 million and $7.4 million, respectively.

[5] Derivative instruments in an asset or liability position are included within Other assets or Other liabilities, respectively, in the balance sheets on a net basis where the Company has both a legal right of offset and the intention to settle the contracts on a net basis.