Investments - Appreciation (Depreciation) on Fixed Maturities (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 18,684	$ 18,456
Unrealized Appreciation	1,544	1,218
Unrealized (Depreciation)	(141)	(219)
Total Fair Value	20,087	19,455
Run-off Settlement Annuity Business [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized Appreciation	636	521
Unrealized (Depreciation)	(14)	(38)
Total Fair Value	2,800	2,700
Federal government and agency [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	463	528
Unrealized Appreciation	289	251
Unrealized (Depreciation)	0	0
Total Fair Value	752	779
State and local government [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,451	1,496
Unrealized Appreciation	153	147
Unrealized (Depreciation)	(1)	(2)
Total Fair Value	1,603	1,641
Foreign government [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,890	1,870
Unrealized Appreciation	183	147
Unrealized (Depreciation)	(1)	(3)
Total Fair Value	2,072	2,014
Corporate [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	14,328	14,022
Unrealized Appreciation	869	632
Unrealized (Depreciation)	(130)	(206)
Total Fair Value	15,067	14,448
Mortgage-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	40	48
Unrealized Appreciation	2	2
Unrealized (Depreciation)	(1)	(1)
Total Fair Value	41	49
Other asset-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	512	492
Unrealized Appreciation	48	39
Unrealized (Depreciation)	(8)	(7)
Total Fair Value	$ 552	$ 524