Derivative Instruments - Net Realized and unrealized gains (losses) on derivative instruments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Derivative [Line Items]
Net realized and unrealized gains (losses) on derivative instruments	$ 5,490	$ (7,903)	$ 2,774	$ 57,127
Derivatives not designated as hedging instruments | Investment related derivatives
Derivative [Line Items]
Interest rate exposure	0	(5,120)	781	(2,046)
Foreign exchange exposure	74	(146)	(592)	(1,026)
Credit exposure	(812)	1,684	(959)	1,380
Financial market exposure	(45)	(4,309)	(2,866)	(2,913)
Derivatives not designated as hedging instruments | Other non-investment derivatives
Derivative [Line Items]
Foreign exchange exposure	(347)	4,063	(1,345)	61,494
Credit exposure	4,477	(327)	4,424	1,151
Modified coinsurance funds withheld contract	2,143	(3,748)	3,331	(913)
Life Funds Withheld Assets
Derivative [Line Items]
Net realized and unrealized gains (losses) on derivative instruments	$ (225,610)	$ (126,140)	$ (691,432)	$ (116,333)