Derivative Instruments - Net Realized and unrealized gains (losses) on Derivative Instruments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Derivative [Line Items]
Amount of gain (loss) recognized in income from ineffective portion of fair value hedges	$ 0	$ 1,794
Net realized and unrealized gains (losses) on derivative instruments	16,521	1,810
Derivatives not designated as hedging instruments
Derivative [Line Items]
Total gain (loss) recognized in income from derivatives not designated as hedging instruments	16,521	16
Derivatives not designated as hedging instruments | Investment related derivatives
Derivative [Line Items]
Interest rate exposure	9,637	348
Foreign exchange exposure	(1,362)	3,288
Credit exposure	82	(404)
Financial market exposure	3,041	871
Derivatives not designated as hedging instruments | Financial operations derivatives
Derivative [Line Items]
Credit exposure	0	(4,800)
Derivatives not designated as hedging instruments | Other non-investment derivatives
Derivative [Line Items]
Foreign exchange exposure	2,059	0
Credit exposure	1,346	0
Guaranteed minimum income benefit contract	0	1,624
Modified coinsurance funds withheld contract	1,718	(911)
Life Funds Withheld Assets
Derivative [Line Items]
Net realized and unrealized gains (losses) on derivative instruments	$ (229,367)	$ 0