Investments - Appreciation (Depreciation) on Fixed Maturities (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 19,392	$ 18,456
Unrealized Appreciation	1,901	1,218
Unrealized (Depreciation)	(49)	(219)
Total Fair Value	21,244	19,455
Run-off Settlement Annuity Business [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized Appreciation	752	521
Unrealized (Depreciation)	(2)	(38)
Total Fair Value	2,900	2,700
Federal government and agency [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	452	528
Unrealized Appreciation	298	251
Unrealized (Depreciation)	0	0
Total Fair Value	750	779
State and local government [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,360	1,496
Unrealized Appreciation	148	147
Unrealized (Depreciation)	0	(2)
Total Fair Value	1,508	1,641
Foreign government [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,104	1,870
Unrealized Appreciation	221	147
Unrealized (Depreciation)	(3)	(3)
Total Fair Value	2,322	2,014
Corporate [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	15,015	14,022
Unrealized Appreciation	1,192	632
Unrealized (Depreciation)	(42)	(206)
Total Fair Value	16,165	14,448
Mortgage-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	35	48
Unrealized Appreciation	2	2
Unrealized (Depreciation)	(1)	(1)
Total Fair Value	36	49
Other asset-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	426	492
Unrealized Appreciation	40	39
Unrealized (Depreciation)	(3)	(7)
Total Fair Value	$ 463	$ 524