Investments Schedule of Credit Quality of Fixed Maturity Security Portfolio by NAIC Designation (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Investment Holdings [Line Items]
Percentage of Investment Grade Fixed Maturity Securities, at Fair Value	98.00%
Fixed Maturities [Member]
Investment Holdings [Line Items]
Investment Owned, at Cost	$ 20,212,062	$ 19,624,485
Investment Owned, at Fair Value	22,474,251	21,108,531
National Association of Insurance Commissioners NAIC Credit Rating 1 [Member] | Fixed Maturities [Member]
Investment Holdings [Line Items]
Investment Owned, at Cost	13,007,318	14,359,272
Investment Owned, at Fair Value	14,591,003	15,486,571
National Association of Insurance Commissioners NAIC Credit Rating 2 [Member] | Fixed Maturities [Member]
Investment Holdings [Line Items]
Investment Owned, at Cost	6,846,088	4,894,739
Investment Owned, at Fair Value	7,538,539	5,272,759
National Association of Insurance Commissioners NAIC Credit Rating 3 [Member] | Fixed Maturities [Member]
Investment Holdings [Line Items]
Investment Owned, at Cost	319,697	335,642
Investment Owned, at Fair Value	304,463	315,406
National Association of Insurance Commissioners NAIC Credit Rating 4 [Member] | Fixed Maturities [Member]
Investment Holdings [Line Items]
Investment Owned, at Cost	31,719	26,674
Investment Owned, at Fair Value	32,361	23,989
National Association of Insurance Commissioners NAIC Credit Rating 5 [Member] | Fixed Maturities [Member]
Investment Holdings [Line Items]
Investment Owned, at Cost	4,451	4,932
Investment Owned, at Fair Value	4,006	5,756
National Association of Insurance Commissioners NAIC Credit Rating 6 [Member] | Fixed Maturities [Member]
Investment Holdings [Line Items]
Investment Owned, at Cost	2,789	3,226
Investment Owned, at Fair Value	$ 3,879	$ 4,050