Derivative Instruments - Narrative (Details) - USD ($) $ in Thousands		3 Months Ended				9 Months Ended
		Sep. 30, 2015		Sep. 30, 2014		Sep. 30, 2015		Sep. 30, 2014		Dec. 31, 2014
Derivative [Line Items]
Cumulative net realized and unrealized loss on life retrocession embedded derivative		$ 468,200				$ 468,200
Gross amounts recognized in balance sheet		74,115				74,115				$ 136,659
Net realized and unrealized gains (losses) on derivative instruments		(7,903)		$ 5,131		57,127		$ 18,540
Gross amounts not offset in the balance sheet - cash collateral		24,000				24,000				78,580
Net results from structured products		4,437	[1]	5,291	[2]	14,719	[3]	48,129	[4]
Fair value hedges | Deposit liabilities
Derivative [Line Items]
Remaining balance		131,734		$ 140,153		131,734		$ 140,153
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		677,094				677,094				592,791
Gross amounts recognized in balance sheet	[5]	25,341				25,341				14,797
Other non-investment derivatives | Derivatives not designated as hedging instruments | Other credit derivatives
Derivative [Line Items]
Asset derivative notional amount		30,075				30,075				31,060
Gross amounts recognized in balance sheet		141				$ 141				$ 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 $15.6 million and $11.1 million, respectively.

[2] The net results from P&C structured products include net investment income and interest credit of $16.8 million and $11.1 million, respectively.

[3] The net results from P&C structured products include net investment income and interest expense of $46.7 million and $31.7 million, respectively.

[4] The net results from P&C structured products include net investment income and interest credit of $52.5 million and $3.7 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.