Derivative Instruments - Net Realized and unrealized gains (losses) on Derivative Instruments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Derivative [Line Items]
Amount of gain (loss) recognized in income from ineffective portion of fair value hedges	$ 0	$ (2,050)	$ 0	$ (256)
Net realized and unrealized gains (losses) on derivative instruments	48,509	11,599	65,030	13,409
Derivatives not designated as hedging instruments
Derivative [Line Items]
Total gain (loss) recognized in income from derivatives not designated as hedging instruments	48,509	13,649	65,030	13,665
Derivatives not designated as hedging instruments | Investment related derivatives
Derivative [Line Items]
Interest rate exposure	(6,563)	8,978	3,073	9,326
Foreign exchange exposure	482	(1,490)	(880)	1,798
Credit exposure	(386)	411	(305)	7
Financial market exposure	(1,645)	2,508	1,398	3,378
Derivatives not designated as hedging instruments | Financial operations derivatives
Derivative [Line Items]
Credit exposure	0	447	0	(4,353)
Derivatives not designated as hedging instruments | Other non-investment derivatives
Derivative [Line Items]
Foreign exchange exposure	55,372	0	57,431	0
Credit exposure	132	0	1,478	0
Guaranteed minimum income benefit contract	0	633	0	2,257
Modified coinsurance funds withheld contract	1,117	2,162	2,835	1,252
Life Funds Withheld Assets
Derivative [Line Items]
Net realized and unrealized gains (losses) on derivative instruments	$ 239,174	$ (17,546)	$ 9,807	$ (17,546)