Derivative Instruments - Gross amounts of derivative fair values contained in the consolidated balance sheet (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Derivatives designated as hedging instruments
Derivatives, Fair Value [Line Items]
Asset derivative notional amount	$ 2,731,749		$ 670,751
Asset derivative fair value	104,733	[1]	12,511	[1]
Liability derivative notional amount	615,505		2,382,507
Liability derivative fair value	23,291	[1]	23,715	[1]
Derivatives designated as hedging instruments | Foreign exchange contracts
Derivatives, Fair Value [Line Items]
Asset derivative notional amount	2,731,749		670,751
Asset derivative fair value	104,733	[1]	12,511	[1]
Liability derivative notional amount	615,505		2,382,507
Liability derivative fair value	23,291	[1]	23,715	[1]
Derivatives not designated as hedging instruments
Derivatives, Fair Value [Line Items]
Asset derivative notional amount	264,901		253,183
Asset derivative fair value	4,012	[1]	12,331	[1]
Liability derivative notional amount	579,205		650,411
Liability derivative fair value	38,103	[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	30,009		45,604
Asset derivative fair value	2,177	[1]	2,060	[1]
Liability derivative notional amount	4,446		26,139
Liability derivative fair value	46	[1]	253	[1]
Derivatives not designated as hedging instruments | Investment related derivatives | Foreign exchange contracts
Derivatives, Fair Value [Line Items]
Asset derivative notional amount	62,824		33,007
Asset derivative fair value	735	[1]	226	[1]
Liability derivative notional amount	14,266		54,449
Liability derivative fair value	608	[1]	1,790	[1]
Derivatives not designated as hedging instruments | Investment related derivatives | Credit exposure
Derivatives, Fair Value [Line Items]
Asset derivative notional amount	13,000		25,000
Asset derivative fair value	23	[1]	486	[1]
Liability derivative notional amount	438,959		436,959
Liability derivative fair value	15,749	[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	83,627		72,597
Asset derivative fair value	1,077	[1]	9,559	[1]
Liability derivative notional amount	15,562		16,910
Liability derivative fair value	1	[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	43,419	[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	62,553		69,051
Liability derivative fair value	21,699	[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	75,441		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".