Investments - Appreciation (Depreciation) on Fixed Maturities (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 18,745	$ 18,456
Unrealized Appreciation	1,860	1,218
Unrealized (Depreciation)	(67)	(219)
Total Fair Value	20,538	19,455
Run-off Settlement Annuity Business [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized Appreciation	738	521
Unrealized (Depreciation)	(4)	(38)
Total Fair Value	2,900	2,700
Federal government and agency [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	448	528
Unrealized Appreciation	303	251
Unrealized (Depreciation)	0	0
Total Fair Value	751	779
State and local government [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,411	1,496
Unrealized Appreciation	165	147
Unrealized (Depreciation)	0	(2)
Total Fair Value	1,576	1,641
Foreign government [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,062	1,870
Unrealized Appreciation	209	147
Unrealized (Depreciation)	(1)	(3)
Total Fair Value	2,270	2,014
Corporate [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	14,328	14,022
Unrealized Appreciation	1,145	632
Unrealized (Depreciation)	(61)	(206)
Total Fair Value	15,412	14,448
Mortgage-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	37	48
Unrealized Appreciation	1	2
Unrealized (Depreciation)	0	(1)
Total Fair Value	38	49
Other asset-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	459	492
Unrealized Appreciation	37	39
Unrealized (Depreciation)	(5)	(7)
Total Fair Value	$ 491	$ 524