Investment Holding Level 4 Available-for-Sale Securities (Details) $ in Millions	5 Months Ended	7 Months Ended	12 Months Ended
	May 31, 2018 USD ($)	Dec. 31, 2018 USD ($) security	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Debt Securities, Available-for-sale [Line Items]
Proceeds from Sale of Debt Securities, Available-for-sale	$ 4,397	$ 3,303	$ 10,315	$ 10,152
Debt Securities, Available-for-sale, Amortized Cost		14,035	20,914
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax		53	1,958
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax		(279)	(73)
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties, Fair Value
Debt Securities, Available-for-sale		13,839	22,799
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities		1	1
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties, Cost		19,839
Available-for-sale Equity Securities, Amortized Cost Basis			140
Equity securities, AFS		0	154
Available-for-sale Securities, Amortized Cost Basis		14,035	21,054
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax		53	1,972
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax		279	73
Available-for-sale Securities		13,839	22,953
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Amortized Cost		481	844
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value		479	850
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Amortized Cost		1,508	3,498
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Fair Value		1,501	3,580
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Amortized Cost		1,807	3,178
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Fair Value		1,783	3,321
Debt Securities, Available-for-sale, Allocated and Single Maturity Date, Maturity, after 10 Years, Amortized Cost		6,311	8,238
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after 10 Years, Fair Value		6,157	9,830
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost		10,107	15,758
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value		9,920	17,581
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost		3,928	5,156
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Fair Value		$ 3,919	5,218
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Amortized Cost			2,751
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value			2,731
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss			20
Available-for-sale Securities Continuous Unrealized Loss Position Twelve Months or Longer Amortized Cost			1,495
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value			1,442
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss			53
Available-for-sale Securities Continuous Unrealized Loss Position Amortized Cost			4,246
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value			4,173
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss			73
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | security		2,234
Percentage of Gross Unrealized Losses Depressed Less than Twenty Percent of Cost or Amortized Cost		99.00%
Available-for-sale Securities, Gross Realized Gains	49	$ 12	226	211
Available-for-sale Securities, Gross Realized Losses	(112)	(38)	(58)	(93)
Asset-backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale		516	819
Collateralized Debt Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale		963	888
Commercial Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale		1,407	2,084
Corporate Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale		7,678	14,038
Debt Security, Government, Non-US [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale		377	407
US States and Political Subdivisions Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale		734	1,266
Residential Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale		1,033	1,427
US Treasury Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale		1,131	1,870
Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Proceeds from Sale of Debt Securities, Available-for-sale	3,523	2,523	7,979	7,409
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Available-for-sale Securities, Gross Realized Gains	45	12	211	206
Available-for-sale Securities, Gross Realized Losses	$ (47)	(37)	(56)	(85)
Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Proceeds from Sale of Debt Securities, Available-for-sale			203	321
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Available-for-sale Securities, Gross Realized Gains			13	4
Available-for-sale Securities, Gross Realized Losses			(1)	$ (8)
Asset-backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost		514	821
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax		2	9
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax		0	(11)
Debt Securities, Available-for-sale		516	819
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities		0	0
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Amortized Cost		179	158
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		179	157
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		0	1
Available-for-sale Securities Continuous Unrealized Loss Position Twelve Months or Longer Amortized Cost		0	219
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		0	209
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0	10
Available-for-sale Securities Continuous Unrealized Loss Position Amortized Cost		179	377
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		179	366
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		0	11
Collateralized Debt Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost		971	886
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax		5	2
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax		(13)	0
Debt Securities, Available-for-sale		963	888
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities		0	0
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Amortized Cost		887	242
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		874	242
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		13	0
Available-for-sale Securities Continuous Unrealized Loss Position Twelve Months or Longer Amortized Cost		0	37
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		0	37
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0	0
Available-for-sale Securities Continuous Unrealized Loss Position Amortized Cost		887	279
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		874	279
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		13	0
Commercial Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost		1,409	2,061
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax		8	45
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax		(7)	(22)
Debt Securities, Available-for-sale		1,407	2,084
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities		0	1
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Amortized Cost		762	524
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		754	517
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		7	7
Available-for-sale Securities Continuous Unrealized Loss Position Twelve Months or Longer Amortized Cost		0	346
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		0	331
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0	15
Available-for-sale Securities Continuous Unrealized Loss Position Amortized Cost		762	870
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		754	848
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		7	22
Corporate Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost		7,860	12,587
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax		19	1,483
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax		(236)	(32)
Debt Securities, Available-for-sale		7,678	14,038
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities		1	0
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Amortized Cost		6,748	1,082
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		6,549	1,074
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		236	8
Available-for-sale Securities Continuous Unrealized Loss Position Twelve Months or Longer Amortized Cost		0	779
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		0	755
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0	24
Available-for-sale Securities Continuous Unrealized Loss Position Amortized Cost		6,748	1,861
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		6,549	1,829
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		236	32
Debt Security, Government, Non-US [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost			379
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax		3	30
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax		(6)	(2)
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties, Fair Value		377
Debt Securities, Available-for-sale			407
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities		0	0
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties, Cost		383
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Amortized Cost		218	60
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		212	59
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		6	1
Available-for-sale Securities Continuous Unrealized Loss Position Twelve Months or Longer Amortized Cost		0	35
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		0	34
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0	1
Available-for-sale Securities Continuous Unrealized Loss Position Amortized Cost		218	95
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		212	93
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		6	2
Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost			1,125
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax		5	142
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax		(10)	(1)
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties, Fair Value		734
Debt Securities, Available-for-sale			1,266
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities		0	0
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties, Cost		738
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Amortized Cost		490	9
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		480	9
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		10	0
Available-for-sale Securities Continuous Unrealized Loss Position Twelve Months or Longer Amortized Cost		0	10
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		0	9
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0	1
Available-for-sale Securities Continuous Unrealized Loss Position Amortized Cost		490	19
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		480	18
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		10	1
Residential Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost		1,034	1,388
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax		3	41
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax		(4)	(2)
Debt Securities, Available-for-sale		1,033	1,427
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities		0	0
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Amortized Cost		727	288
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		723	287
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		4	1
Available-for-sale Securities Continuous Unrealized Loss Position Twelve Months or Longer Amortized Cost		0	28
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		0	27
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0	1
Available-for-sale Securities Continuous Unrealized Loss Position Amortized Cost		727	316
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		723	314
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		4	2
US Treasury Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost		1,126	1,667
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax		8	206
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax		(3)	(3)
Debt Securities, Available-for-sale		1,131	1,870
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities		0	0
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Amortized Cost		619	382
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		616	380
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		3	2
Available-for-sale Securities Continuous Unrealized Loss Position Twelve Months or Longer Amortized Cost		0	38
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		0	37
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0	1
Available-for-sale Securities Continuous Unrealized Loss Position Amortized Cost		619	420
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		616	417
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		3	3
Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities			0
Available-for-sale Equity Securities, Amortized Cost Basis			140
Available-for-sale Equity Securities, Accumulated Gross Unrealized Gain, before Tax			14
Available-for-sale Equity Securities, Accumulated Gross Unrealized Loss, before Tax			0
Equity securities, AFS			154
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Amortized Cost			6
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value			6
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss			0
Available-for-sale Securities Continuous Unrealized Loss Position Twelve Months or Longer Amortized Cost			3
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value			3
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss			0
Available-for-sale Securities Continuous Unrealized Loss Position Amortized Cost			9
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value			9
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss			0
Debt Securities [Member]
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Amortized Cost		10,630	2,745
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		10,387	2,725
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		279	20
Available-for-sale Securities Continuous Unrealized Loss Position Twelve Months or Longer Amortized Cost		0	1,492
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		0	1,439
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0	53
Available-for-sale Securities Continuous Unrealized Loss Position Amortized Cost		10,630	4,237
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		10,387	4,164
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		$ 279	$ 73