Fair Value Measurements (Details 3) (USD $) In Thousands, unless otherwise specified						12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Recurring basis Level 3	Dec. 31, 2011 Recurring basis Level 3	Dec. 31, 2012 Fixed maturities available-for-sale, Asset-backed securities Recurring basis Level 3 Internal model pricing	Dec. 31, 2012 Fixed maturities available-for-sale, Asset-backed securities Recurring basis Level 3 Internal model pricing Weighted average item	Dec. 31, 2012 Fixed maturities available-for-sale, Asset-backed securities Recurring basis Level 3 Internal model pricing Minimum	Dec. 31, 2012 Fixed maturities available-for-sale, Asset-backed securities Recurring basis Level 3 Internal model pricing Maximum
Significant unobservable inputs used during the valuation of assets categorized within Level 3 of the recurring fair value measurements table
Fixed maturities available-for-sale	$ 18,188,344	$ 16,589,783	$ 267,392	$ 315,539	$ 265,470
Unobservable Input
Prepayment speed assumption (as a percent)						5.00%
Constant default rate assumption (as a percent)						5.00%	1.20%	7.90%
Adjusted ABX Index spread assumption						655
Internally calculated liquidity premium adjustment included in Adjusted ABX Index spread assumption						217
Overall discount rate (as a percent)							384.00%	918.00%