Derivative Instruments - Earnings relating to derivative instruments not formally designated as hedging instruments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Derivative Instruments Gain Loss [Line Items]
Total derivatives not designated as hedging instruments	$ 53,123	$ 30,142	$ 7,301
Amount of gain (loss) recognized in income from ineffective portion of fair value hedges	0	(256)	497
Net realized and unrealized gains (losses) on life retrocession embedded derivative and derivative instruments - Life Funds Withheld Assets	53,123	29,886	7,798
Not Designated as Hedging Instrument | Investment Related Derivatives
Derivative Instruments Gain Loss [Line Items]
Interest rate exposure	(2,347)	15,959	5,065
Foreign exchange exposure	(1,542)	3,351	(948)
Credit exposure	(2,537)	400	(4,052)
Financial market exposure	(2,190)	411	6,302
Not Designated as Hedging Instrument | Financial Operations Derivatives
Derivative Instruments Gain Loss [Line Items]
Credit exposure	0	5,023	(2,437)
Not Designated as Hedging Instrument | Other Non Investment Derivatives
Derivative Instruments Gain Loss [Line Items]
Foreign exchange exposure	60,319	0	0
Credit exposure	1,375	0
Contingent capital facility			0
Guaranteed minimum income benefit contract	0	2,257	10,457
Modified coinsurance funds withheld contract	45	2,741	(7,086)
Life Funds Withheld Assets [Member]
Derivative Instruments Gain Loss [Line Items]
Net realized and unrealized gains (losses) on life retrocession embedded derivative and derivative instruments - Life Funds Withheld Assets	$ (151,691)	$ (488,222)	$ 0