Derivative Instruments - Net Realized and unrealized gains (losses) on Derivative Instruments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Derivative [Line Items]
Amount of gain (loss) recognized in income from ineffective portion of fair value hedges	$ (260)	$ (197)	$ 709	$ (4,830)
Net realized and unrealized gains (losses) on derivative instruments	880	6,254	3,660	2,656
Derivatives not designated as hedging instruments
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	1,140	6,451	2,951	7,486
Derivatives not designated as hedging instruments | Investment related derivatives
Derivative [Line Items]
Interest rate exposure	4,334	243	4,822	860
Foreign exchange exposure	3,710	1,218	(578)	1,547
Credit exposure	(956)	(2,281)	(2,950)	343
Financial market exposure	1,553	2,337	4,170	312
Derivatives not designated as hedging instruments | Financial operations derivatives
Derivative [Line Items]
Credit exposure	(3,980)	0	(2,651)	143
Derivatives not designated as hedging instruments | Other non-investment derivatives
Derivative [Line Items]
Guaranteed minimum income benefit contract	175	885	6,178	1,971
Gain Loss On Modified Coinsurance Funds Withheld Contract Not Designated As Hedging Instruments	$ (3,696)	$ 4,049	$ (6,040)	$ 2,310