Derivative Instruments - Net Realized and unrealized gains (losses) on Derivative Instruments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Derivative [Line Items]
Amount of gain (loss) recognized in income from ineffective portion of fair value hedges	$ 1,794	$ 1,475
Net realized and unrealized gains (losses) on derivative instruments	1,810	7,885
Derivatives not designated as hedging instruments
Derivative [Line Items]
Total gain (loss) recognized in income from derivatives not designated as hedging instruments	16	6,410
Derivatives not designated as hedging instruments | Investment related derivatives
Derivative [Line Items]
Interest rate exposure	348	200
Foreign exchange exposure	3,288	(1,598)
Credit exposure	(404)	(816)
Financial market exposure	871	5,353
Derivatives not designated as hedging instruments | Financial operations derivatives
Derivative [Line Items]
Credit exposure	(4,800)	242
Derivatives not designated as hedging instruments | Other non-investment derivatives
Derivative [Line Items]
Guaranteed minimum income benefit contract	1,624	3,697
Modified coinsurance funds withheld contract	$ (911)	$ (668)