Investments - Unrealized Losses on AFS Securities (Details) - USD ($) $ in Millions	Sep. 30, 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	$ 273	158
12 Months or More	0	219
Total	273	377
Fair Value
Less Than 12 Months	272	157
12 Months or More	0	209
Total	272	366
Unrealized Losses
Less Than 12 Months	(1)	(1)
12 Months or More	0	(10)
Total	(1)	(11)
CDOs
Amortized Cost
Less Than 12 Months	509	242
12 Months or More	0	37
Total	509	279
Fair Value
Less Than 12 Months	508	242
12 Months or More	0	37
Total	508	279
Unrealized Losses
Less Than 12 Months	(1)	0
12 Months or More	0	0
Total	(1)	0
CMBS
Amortized Cost
Less Than 12 Months	1,180	524
12 Months or More	0	346
Total	1,180	870
Fair Value
Less Than 12 Months	1,162	517
12 Months or More	0	331
Total	1,162	848
Unrealized Losses
Less Than 12 Months	(15)	(7)
12 Months or More	0	(15)
Total	(15)	(22)
Corporate
Amortized Cost
Less Than 12 Months	6,646	1,082
12 Months or More	0	779
Total	6,646	1,861
Fair Value
Less Than 12 Months	6,570	1,074
12 Months or More	0	755
Total	6,570	1,829
Unrealized Losses
Less Than 12 Months	(110)	(8)
12 Months or More	0	(24)
Total	(110)	(32)
Foreign government/government agencies
Amortized Cost
Less Than 12 Months	111	60
12 Months or More	0	35
Total	111	95
Fair Value
Less Than 12 Months	107	59
12 Months or More	0	34
Total	107	93
Unrealized Losses
Less Than 12 Months	(3)	(1)
12 Months or More	0	(1)
Total	(3)	(2)
Municipal
Amortized Cost
Less Than 12 Months	655	9
12 Months or More	0	10
Total	655	19
Fair Value
Less Than 12 Months	641	9
12 Months or More	0	9
Total	641	18
Unrealized Losses
Less Than 12 Months	(15)	0
12 Months or More	0	(1)
Total	(15)	(1)
RMBS [Member]
Amortized Cost
Less Than 12 Months	619	288
12 Months or More	0	28
Total	619	316
Fair Value
Less Than 12 Months	615	287
12 Months or More	0	27
Total	615	314
Unrealized Losses
Less Than 12 Months	(4)	(1)
12 Months or More	0	(1)
Total	(4)	(2)
U.S. Treasuries
Amortized Cost
Less Than 12 Months	1,302	382
12 Months or More	0	38
Total	1,302	420
Fair Value
Less Than 12 Months	1,262	380
12 Months or More	0	37
Total	1,262	417
Unrealized Losses
Less Than 12 Months	(40)	(2)
12 Months or More	0	(1)
Total	(40)	(3)
Fixed maturities
Amortized Cost
Less Than 12 Months	11,295	2,745
12 Months or More	0	1,492
Total	11,295	4,237
Fair Value
Less Than 12 Months	11,137	2,725
12 Months or More	0	1,439
Total	11,137	4,164
Unrealized Losses
Less Than 12 Months	(189)	(20)
12 Months or More	0	(53)
Total	$ (189)	(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