Derivative Instruments - Net Realized and unrealized gains (losses) on Derivative Instruments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Derivative [Line Items]
Amount of gain (loss) recognized in income from ineffective portion of fair value hedges	$ (506)	$ (2,194)	$ 969	$ (4,633)
Net realized and unrealized gains (losses) on derivative instruments	(5,105)	(4,301)	2,780	(3,598)
Derivatives not designated as hedging instruments
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(4,599)	(2,107)	1,811	1,035
Derivatives not designated as hedging instruments | Investment related derivatives
Derivative [Line Items]
Interest rate exposure	288	(83)	488	617
Foreign exchange exposure	(2,690)	683	(4,288)	329
Credit exposure	(1,178)	6,323	(1,994)	2,624
Financial market exposure	(2,736)	(5,970)	2,617	(2,025)
Derivatives not designated as hedging instruments | Financial operations derivatives
Derivative [Line Items]
Credit exposure	1,087	0	1,329	143
Derivatives not designated as hedging instruments | Other non-investment derivatives
Derivative [Line Items]
Guaranteed minimum income benefit contract	2,306	(929)	6,003	1,086
Gain Loss On Modified Coinsurance Funds Withheld Contract Not Designated As Hedging Instruments	$ (1,676)	$ (2,131)	$ (2,344)	$ (1,739)