Derivative Instruments - Gross amounts of derivative fair values contained in the consolidated balance sheet (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013		Dec. 31, 2012
Derivatives, Fair Value [Line Items]
Asset derivative fair value	$ 17,847		$ 23,515
Liability derivative fair value	37,321		65,299
Derivatives designated as hedging instruments
Derivatives, Fair Value [Line Items]
Asset derivative notional amount	1,914,366		670,751
Asset derivative fair value	14,563	[1]	12,511	[1]
Liability derivative notional amount	1,483,052		2,382,507
Liability derivative fair value	3,336	[1]	23,715	[1]
Derivatives designated as hedging instruments | Foreign exchange contracts
Derivatives, Fair Value [Line Items]
Asset derivative notional amount	1,914,366		670,751
Asset derivative fair value	14,563	[1]	12,511	[1]
Liability derivative notional amount	1,483,052		2,382,507
Liability derivative fair value	3,336	[1]	23,715	[1]
Derivatives not designated as hedging instruments
Derivatives, Fair Value [Line Items]
Asset derivative notional amount	552,994		253,183
Asset derivative fair value	5,111	[1]	12,331	[1]
Liability derivative notional amount	546,367		650,411
Liability derivative fair value	35,812	[1]	42,911	[1]
Derivatives not designated as hedging instruments | Investment related derivatives | Interest rate exposure
Derivatives, Fair Value [Line Items]
Asset derivative notional amount	380,930		45,604
Asset derivative fair value	3,249	[1]	2,060	[1]
Liability derivative notional amount	5,417		26,139
Liability derivative fair value	0	[1]	253	[1]
Derivatives not designated as hedging instruments | Investment related derivatives | Foreign exchange contracts
Derivatives, Fair Value [Line Items]
Asset derivative notional amount	32,120		33,007
Asset derivative fair value	452	[1]	226	[1]
Liability derivative notional amount	31,928		54,449
Liability derivative fair value	1,487	[1]	1,790	[1]
Derivatives not designated as hedging instruments | Investment related derivatives | Credit exposure
Derivatives, Fair Value [Line Items]
Asset derivative notional amount	10,310		25,000
Asset derivative fair value	97	[1]	486	[1]
Liability derivative notional amount	392,710		436,959
Liability derivative fair value	14,931	[1]	15,472	[1]
Derivatives not designated as hedging instruments | Investment related derivatives | Financial market exposure
Derivatives, Fair Value [Line Items]
Asset derivative notional amount	56,687		72,597
Asset derivative fair value	1,313	[1]	9,559	[1]
Liability derivative notional amount	14,882		16,910
Liability derivative fair value	0	[1]	0	[1]
Derivatives not designated as hedging instruments | Financial operations derivatives | Credit exposure
Derivatives, Fair Value [Line Items]
Asset derivative notional amount	0	[2]	0	[2]
Asset derivative fair value	0	[1],[2]	0	[1],[2]
Liability derivative notional amount	43,998	[2]	46,903	[2]
Liability derivative fair value	0	[1],[2]	0	[1],[2]
Derivatives not designated as hedging instruments | Other non-investment derivatives | Guaranteed minimum income benefit contract
Derivatives, Fair Value [Line Items]
Asset derivative notional amount	0		0
Asset derivative fair value	0	[1]	0	[1]
Liability derivative notional amount	57,432		69,051
Liability derivative fair value	19,394	[1]	25,396	[1]
Derivatives not designated as hedging instruments | Other non-investment derivatives | Modified coinsurance funds withheld contract
Derivatives, Fair Value [Line Items]
Asset derivative notional amount	72,947		76,975
Asset derivative fair value	0	[1]	0	[1]
Liability derivative notional amount	0		0
Liability derivative fair value	$ 0	[1]	$ 0	[1]

[1] Derivative instruments in an asset or liability position are included within Other assets or Other liabilities, respectively, in the balance sheet on a net basis where the Company has both a legal right of offset and the intentions to settle the contracts on a net basis.

[2] Financial operations derivatives represent interests in variable interest entities as described in Note 10, “Variable Interest Entities".