Investments - Appreciation (Depreciation) on Fixed Maturities (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 18,456	$ 17,278
Unrealized Appreciation	1,218	1,747
Unrealized (Depreciation)	(219)	(42)
Total Fair Value	19,455	18,983
Commitments to purchase fixed maturities	15
Run-off Settlement Annuity Business [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized Appreciation	521	758
Unrealized (Depreciation)	(38)	(2)
Total Fair Value	2,700	3,100
Federal government and agency [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	528	608
Unrealized Appreciation	251	346
Unrealized (Depreciation)	0	0
Total Fair Value	779	954
State and local government [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,496	1,682
Unrealized Appreciation	147	176
Unrealized (Depreciation)	(2)	(2)
Total Fair Value	1,641	1,856
Foreign government [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,870	1,824
Unrealized Appreciation	147	121
Unrealized (Depreciation)	(3)	(5)
Total Fair Value	2,014	1,940
Corporate [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	14,022	12,517
Unrealized Appreciation	632	1,014
Unrealized (Depreciation)	(206)	(33)
Total Fair Value	14,448	13,498
Mortgage-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	48	83
Unrealized Appreciation	2	3
Unrealized (Depreciation)	(1)	(1)
Total Fair Value	49	85
Other asset-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	492	564
Unrealized Appreciation	39	87
Unrealized (Depreciation)	(7)	(1)
Total Fair Value	$ 524	$ 650