Derivative Instruments - Net Realized and unrealized gains (losses) on derivative instruments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Derivative [Line Items]
Net realized and unrealized gains (losses) on derivative instruments	$ 906	$ 48,509	$ (2,716)	$ 65,030
Derivatives not designated as hedging instruments | Investment related derivatives
Derivative [Line Items]
Interest rate exposure	0	(6,563)	781	3,073
Foreign exchange exposure	4	482	(666)	(880)
Credit exposure	16	(386)	(147)	(305)
Financial market exposure	(1,811)	(1,645)	(2,821)	1,398
Derivatives not designated as hedging instruments | Other non-investment derivatives
Derivative [Line Items]
Foreign exchange exposure	183	55,372	(998)	57,431
Credit exposure	250	132	(53)	1,478
Modified coinsurance funds withheld contract	2,264	1,117	1,188	2,835
Life Funds Withheld Assets
Derivative [Line Items]
Net realized and unrealized gains (losses) on derivative instruments	$ (229,742)	$ 239,174	$ (465,822)	$ 9,807