Derivative Instruments - Net Realized and unrealized gains (losses) on derivative instruments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Derivative [Line Items]
Net realized and unrealized gains (losses) on derivative instruments	$ (7,069)	$ (3,622)
Derivatives not designated as hedging instruments | Investment related derivatives
Derivative [Line Items]
Interest rate exposure	(214)	781
Foreign currency exposure	(745)	(670)
Credit exposure	(854)	(163)
Financial market exposure	185	(1,010)
Derivatives not designated as hedging instruments | Other non-investment derivatives
Derivative [Line Items]
Foreign currency exposure	(1,210)	(1,181)
Credit exposure	632	(303)
Modified coinsurance funds withheld contract, including life retrocession embedded derivative	(3,925)	(1,076)
Gain Loss On Other Not Designated As Hedging Instruments	(938)	0
Life Funds Withheld Assets
Derivative [Line Items]
Net realized and unrealized gains (losses) on derivative instruments	$ (50,101)	$ (236,080)