Investments (Fair Value and Losses by Investment Category and Length of Time in a Loss Position) (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 21,430	$ 21,494
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	844	828
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	29,404	28,394
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	6,090	5,556
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	50,834	49,888
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	6,934	6,384
Investment grade securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	20,417	21,046
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	807	820
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	28,934	27,877
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	6,001	5,463
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	49,351	48,923
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	6,808	6,283
Non-investment grade securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	1,013	448
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	37	8
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	470	517
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	89	93
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	1,483	965
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	126	101
Corporate Debt Securities [Member] | Investment grade securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	14,571	14,741
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	601	529
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	18,829	18,851
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	3,587	3,682
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	33,400	33,592
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	4,188	4,211
Corporate Debt Securities [Member] | Non-investment grade securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	962	347
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	33	7
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	322	347
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	50	50
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	1,284	694
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	83	57
Canadian and Canadian provincial governments | Investment grade securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	645	286
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	18	5
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	411	469
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	63	46
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	1,056	755
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	81	51
Residential mortgage-backed securities | Investment grade securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	218	354
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	3	7
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	587	593
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	83	100
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	805	947
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	86	107
Asset-backed Securities [Member] | Investment grade securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	1,612	940
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	20	19
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	1,373	1,730
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	139	159
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	2,985	2,670
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	159	178
Asset-backed Securities [Member] | Non-investment grade securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	51	101
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	4	1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	17	40
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1	5
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	68	141
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	5	6
Commercial mortgage-backed securities | Investment grade securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	207	333
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	6	4
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	843	980
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	68	91
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	1,050	1,313
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	74	95
US Government Agencies Debt Securities [Member] | Investment grade securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	89	792
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	3	15
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	649	656
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	254	266
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	738	1,448
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	257	281
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]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	104	155
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	3	7
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	417	417
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	86	92
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	521	572
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	89	99
Debt Security, Government, Non-US [Member] | Investment grade securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	1,341	1,408
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	58	42
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	1,736	1,816
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	350	344
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	3,077	3,224
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	408	386
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]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	131	130
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	38	38
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	131	130
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	38	38
JAPAN | Investment grade securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	1,630	2,037
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	95	192
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	4,089	2,365
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1,371	683
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	5,719	4,402
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 1,466	$ 875