Investments - Unrealized Losses on AFS Securities (Details) - USD ($) $ in Millions	Jun. 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	$ 295	158
12 Months or More	0	219
Total	295	377
Fair Value
Less Than 12 Months	293	157
12 Months or More	0	209
Total	293	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	451	242
12 Months or More	0	37
Total	451	279
Fair Value
Less Than 12 Months	451	242
12 Months or More	0	37
Total	451	279
Unrealized Losses
Less Than 12 Months	0	0
12 Months or More	0	0
Total	0	0
CMBS
Amortized Cost
Less Than 12 Months	1,115	524
12 Months or More	0	346
Total	1,115	870
Fair Value
Less Than 12 Months	1,106	517
12 Months or More	0	331
Total	1,106	848
Unrealized Losses
Less Than 12 Months	(6)	(7)
12 Months or More	0	(15)
Total	(6)	(22)
Corporate
Amortized Cost
Less Than 12 Months	7,286	1,082
12 Months or More	0	779
Total	7,286	1,861
Fair Value
Less Than 12 Months	7,223	1,074
12 Months or More	0	755
Total	7,223	1,829
Unrealized Losses
Less Than 12 Months	(97)	(8)
12 Months or More	0	(24)
Total	(97)	(32)
Foreign government/government agencies
Amortized Cost
Less Than 12 Months	178	60
12 Months or More	0	35
Total	178	95
Fair Value
Less Than 12 Months	176	59
12 Months or More	0	34
Total	176	93
Unrealized Losses
Less Than 12 Months	0	(1)
12 Months or More	0	(1)
Total	0	(2)
Municipal
Amortized Cost
Less Than 12 Months	475	9
12 Months or More	0	10
Total	475	19
Fair Value
Less Than 12 Months	472	9
12 Months or More	0	9
Total	472	18
Unrealized Losses
Less Than 12 Months	(3)	0
12 Months or More	0	(1)
Total	(3)	(1)
RMBS [Member]
Amortized Cost
Less Than 12 Months	630	288
12 Months or More	0	28
Total	630	316
Fair Value
Less Than 12 Months	630	287
12 Months or More	0	27
Total	630	314
Unrealized Losses
Less Than 12 Months	(1)	(1)
12 Months or More	0	(1)
Total	(1)	(2)
U.S. Treasuries
Amortized Cost
Less Than 12 Months	1,105	382
12 Months or More	0	38
Total	1,105	420
Fair Value
Less Than 12 Months	1,101	380
12 Months or More	0	37
Total	1,101	417
Unrealized Losses
Less Than 12 Months	(4)	(2)
12 Months or More	0	(1)
Total	(4)	(3)
Fixed maturities
Amortized Cost
Less Than 12 Months	11,535	2,745
12 Months or More	0	1,492
Total	11,535	4,237
Fair Value
Less Than 12 Months	11,452	2,725
12 Months or More	0	1,439
Total	11,452	4,164
Unrealized Losses
Less Than 12 Months	(112)	(20)
12 Months or More	0	(53)
Total	$ (112)	(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