Investments - Unrealized Losses on AFS Securities (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Amortized Cost
Less Than 12 Months		$ 2,751
12 Months or More		1,495
Total		4,246
Fair Value
Less Than 12 Months		2,731
12 Months or More		1,442
Total		4,173
Unrealized Losses
Less Than 12 Months		(20)
12 Months or More		(53)
Total		(73)
ABS [Member]
Amortized Cost
Less Than 12 Months	$ 298	158
12 Months or More	203	219
Total	501	377
Fair Value
Less Than 12 Months	296	157
12 Months or More	195	209
Total	491	366
Unrealized Losses
Less Than 12 Months	(2)	(1)
12 Months or More	(8)	(10)
Total	(10)	(11)
CDOs
Amortized Cost
Less Than 12 Months	582	242
12 Months or More	0	37
Total	582	279
Fair Value
Less Than 12 Months	580	242
12 Months or More	0	37
Total	580	279
Unrealized Losses
Less Than 12 Months	(2)	0
12 Months or More	0	0
Total	(2)	0
CMBS
Amortized Cost
Less Than 12 Months	901	524
12 Months or More	338	346
Total	1,239	870
Fair Value
Less Than 12 Months	881	517
12 Months or More	319	331
Total	1,200	848
Unrealized Losses
Less Than 12 Months	(20)	(7)
12 Months or More	(19)	(15)
Total	(39)	(22)
Corporate
Amortized Cost
Less Than 12 Months	3,701	1,082
12 Months or More	751	779
Total	4,452	1,861
Fair Value
Less Than 12 Months	3,631	1,074
12 Months or More	708	755
Total	4,339	1,829
Unrealized Losses
Less Than 12 Months	(70)	(8)
12 Months or More	(43)	(24)
Total	(113)	(32)
Foreign government/government agencies
Amortized Cost
Less Than 12 Months	175	60
12 Months or More	35	35
Total	210	95
Fair Value
Less Than 12 Months	171	59
12 Months or More	33	34
Total	204	93
Unrealized Losses
Less Than 12 Months	(4)	(1)
12 Months or More	(2)	(1)
Total	(6)	(2)
Municipal
Amortized Cost
Less Than 12 Months	78	9
12 Months or More	10	10
Total	88	19
Fair Value
Less Than 12 Months	77	9
12 Months or More	9	9
Total	86	18
Unrealized Losses
Less Than 12 Months	(1)	0
12 Months or More	(1)	(1)
Total	(2)	(1)
RMBS
Amortized Cost
Less Than 12 Months	526	288
12 Months or More	21	28
Total	547	316
Fair Value
Less Than 12 Months	518	287
12 Months or More	20	27
Total	538	314
Unrealized Losses
Less Than 12 Months	(8)	(1)
12 Months or More	(1)	(1)
Total	(9)	(2)
U.S. Treasuries
Amortized Cost
Less Than 12 Months	386	382
12 Months or More	32	38
Total	418	420
Fair Value
Less Than 12 Months	376	380
12 Months or More	31	37
Total	407	417
Unrealized Losses
Less Than 12 Months	(10)	(2)
12 Months or More	(1)	(1)
Total	(11)	(3)
Fixed maturities
Amortized Cost
Less Than 12 Months	6,647	2,745
12 Months or More	1,390	1,492
Total	8,037	4,237
Fair Value
Less Than 12 Months	6,530	2,725
12 Months or More	1,315	1,439
Total	7,845	4,164
Unrealized Losses
Less Than 12 Months	(117)	(20)
12 Months or More	(75)	(53)
Total	$ (192)	(73)
Equity securities
Amortized Cost
Less Than 12 Months		6
12 Months or More		3
Total		9
Fair Value
Less Than 12 Months		6
12 Months or More		3
Total		9
Unrealized Losses
Less Than 12 Months		0
12 Months or More		0
Total		$ 0