Derivative Instruments - Derivatives Designated As Fair Value Hedges (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income from ineffective portion of fair value hedges	$ 1,794	$ 1,475
Derivatives designated as hedging instruments | Fair value hedges | Net realized and unrealized gains (losses) on derivative instruments
Derivative Instruments, Gain (Loss) [Line Items]
Hedged items - amount of gain (loss) recognized in income attributable to risk	(6,531)	30,245
Amount of gain (loss) recognized in income from ineffective portion of fair value hedges	1,794	1,475
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]
Hedged items - amount of gain (loss) recognized in income attributable to risk	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]
Hedged items - amount of gain (loss) recognized in income attributable to risk	(6,531)	30,245
Derivatives designated as hedging instruments | Fair value hedges | Net realized and unrealized gains (losses) on derivative instruments | Deposit liabilities
Derivative Instruments, Gain (Loss) [Line Items]
Hedged items - amount of gain (loss) recognized in income attributable to risk	0	0
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]
Hedged items - amount of gain (loss) recognized in income attributable to risk	$ 8,325	$ (28,770)