Derivative Instruments - Derivatives Designated As Fair Value Hedges (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income from ineffective portion of fair value hedges	$ (2,050)	$ (506)	$ (256)	$ 969
Derivatives designated as hedging instruments | Fair value hedges | Net realized and unrealized gains (losses) on derivative instruments
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income	(9,132)	(5,002)	(15,663)	25,243
Amount of gain (loss) recognized in income from ineffective portion of fair value hedges	(2,050)	(506)	(256)	969
Derivatives designated as hedging instruments | Fair value hedges | Net realized and unrealized gains (losses) on derivative instruments | Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income	0	0	0	0
Derivatives designated as hedging instruments | Fair value hedges | Net realized and unrealized gains (losses) on derivative instruments | Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income	(9,132)	(5,002)	(15,663)	25,243
Derivatives designated as hedging instruments | Fair value hedges | Net realized and unrealized gains (losses) on derivative instruments | Fixed maturity investments
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income	$ 7,082	$ 4,496	$ 15,407	$ (24,274)