Investments (Fair Value and Losses by Investment Category and Length of Time in a Loss Position) (Details) - Fixed maturity securities - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months	$ 6,118	$ 4,068
Gross Unrealized Losses - Less than 12 months	199	163
Estimated Fair Value - 12 months or greater	1,799	769
Gross Unrealized Losses - 12 months or greater	68	34
Estimated Fair Value	7,917	4,837
Gross Unrealized Losses	267	197
Non-investment grade securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months	348	522
Gross Unrealized Losses - Less than 12 months	46	80
Estimated Fair Value - 12 months or greater	242	113
Gross Unrealized Losses - 12 months or greater	28	15
Estimated Fair Value	590	635
Gross Unrealized Losses	74	95
Investment grade securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months	5,770	3,546
Gross Unrealized Losses - Less than 12 months	153	83
Estimated Fair Value - 12 months or greater	1,557	656
Gross Unrealized Losses - 12 months or greater	40	19
Estimated Fair Value	7,327	4,202
Gross Unrealized Losses	193	102
Corporate Debt Securities [Member] | Non-investment grade securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months	258	375
Gross Unrealized Losses - Less than 12 months	42	49
Estimated Fair Value - 12 months or greater	168	81
Gross Unrealized Losses - 12 months or greater	10	11
Estimated Fair Value	426	456
Gross Unrealized Losses	52	60
Corporate Debt Securities [Member] | Investment grade securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months	2,596	930
Gross Unrealized Losses - Less than 12 months	79	29
Estimated Fair Value - 12 months or greater	168	70
Gross Unrealized Losses - 12 months or greater	6	5
Estimated Fair Value	2,764	1,000
Gross Unrealized Losses	85	34
Residential mortgage-backed securities | Investment grade securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months	261	294
Gross Unrealized Losses - Less than 12 months	5	2
Estimated Fair Value - 12 months or greater	21	0
Gross Unrealized Losses - 12 months or greater	1	0
Estimated Fair Value	282	294
Gross Unrealized Losses	6	2
Asset-backed securities | Non-investment grade securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months	24	20
Gross Unrealized Losses - Less than 12 months	1	13
Estimated Fair Value - 12 months or greater	15	4
Gross Unrealized Losses - 12 months or greater	11	1
Estimated Fair Value	39	24
Gross Unrealized Losses	12	14
Asset-backed securities | Investment grade securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months	800	1,096
Gross Unrealized Losses - Less than 12 months	4	17
Estimated Fair Value - 12 months or greater	754	570
Gross Unrealized Losses - 12 months or greater	5	11
Estimated Fair Value	1,554	1,666
Gross Unrealized Losses	9	28
Commercial mortgage-backed securities | Non-investment grade securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months	0	91
Gross Unrealized Losses - Less than 12 months	0	15
Estimated Fair Value - 12 months or greater	43	0
Gross Unrealized Losses - 12 months or greater	5	0
Estimated Fair Value	43	91
Gross Unrealized Losses	5	15
Commercial mortgage-backed securities | Investment grade securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months	0	160
Gross Unrealized Losses - Less than 12 months	0	6
Estimated Fair Value - 12 months or greater	24	0
Gross Unrealized Losses - 12 months or greater	1	0
Estimated Fair Value	24	160
Gross Unrealized Losses	1	6
US Government Agencies Debt Securities [Member] | Investment grade securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months	364	27
Gross Unrealized Losses - Less than 12 months	24	1
Estimated Fair Value - 12 months or greater	0	0
Gross Unrealized Losses - 12 months or greater	0	0
Estimated Fair Value	364	27
Gross Unrealized Losses	24	1
US States and Political Subdivisions Debt Securities [Member] | Investment grade securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months	95	66
Gross Unrealized Losses - Less than 12 months	2	1
Estimated Fair Value - 12 months or greater	29	16
Gross Unrealized Losses - 12 months or greater	4	3
Estimated Fair Value	124	82
Gross Unrealized Losses	6	4
Debt Security, Government, Non-US [Member] | Non-investment grade securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months	66	36
Gross Unrealized Losses - Less than 12 months	3	3
Estimated Fair Value - 12 months or greater	16	28
Gross Unrealized Losses - 12 months or greater	2	3
Estimated Fair Value	82	64
Gross Unrealized Losses	5	6
Debt Security, Government, Non-US [Member] | Investment grade securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months	1,630	973
Gross Unrealized Losses - Less than 12 months	37	27
Estimated Fair Value - 12 months or greater	561	0
Gross Unrealized Losses - 12 months or greater	23	0
Estimated Fair Value	2,191	973
Gross Unrealized Losses	$ 60	$ 27