Investments - Unrealized Capital Losses (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Fair Value	$ 2,808	$ 2,350
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Accumulated Loss	67	86
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	11,537	11,475
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1,842	2,067
Debt Securities, Available-for-sale, Unrealized Loss Position	14,345	13,825
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 1,909	2,153
Minimum
Available-for-sale Securities Including Securities Pledged [Line Items]
Fixed Maturities Average Duration	6 years
Maximum
Available-for-sale Securities Including Securities Pledged [Line Items]
Fixed Maturities Average Duration	6 years 6 months
U.S. Treasuries
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Fair Value	$ 208	229
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Accumulated Loss	9	16
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	132	127
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	29	34
Debt Securities, Available-for-sale, Unrealized Loss Position	340	356
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	38	50
State, municipalities and political subdivisions
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Fair Value	2	4
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	369	403
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	71	82
Debt Securities, Available-for-sale, Unrealized Loss Position	371	407
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	71	82
U.S. corporate public securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Fair Value	746	615
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Accumulated Loss	33	28
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	3,677	3,626
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	808	868
Debt Securities, Available-for-sale, Unrealized Loss Position	4,423	4,241
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	841	896
U.S. corporate private securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Fair Value	296	405
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Accumulated Loss	4	10
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	2,345	2,260
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	221	254
Debt Securities, Available-for-sale, Unrealized Loss Position	2,641	2,665
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	225	264
Foreign corporate public securities and foreign governments
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Fair Value	430	355
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Accumulated Loss	10	14
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	1,063	1,051
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	203	221
Debt Securities, Available-for-sale, Unrealized Loss Position	1,493	1,406
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	213	235
Foreign corporate private securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Fair Value	434	429
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Accumulated Loss	4	11
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	1,202	1,205
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	95	127
Debt Securities, Available-for-sale, Unrealized Loss Position	1,636	1,634
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	99	138
Residential mortgage-backed
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Fair Value	228	253
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Accumulated Loss	4	6
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	716	704
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	103	122
Debt Securities, Available-for-sale, Unrealized Loss Position	944	957
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	107	128
Commercial mortgage-backed
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Fair Value	65	18
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	1,823	1,888
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	290	333
Debt Securities, Available-for-sale, Unrealized Loss Position	1,888	1,906
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	290	333
Other asset-backed securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Fair Value	399	29
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Accumulated Loss	3	1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	195	197
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	21	24
Debt Securities, Available-for-sale, Unrealized Loss Position	594	226
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	24	25
US Government Corporations and Agencies Securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Fair Value	0
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Accumulated Loss	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	15
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1
Debt Securities, Available-for-sale, Unrealized Loss Position	15
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 1
US Treasury and Government
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Fair Value		13
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Accumulated Loss		0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer		14
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		2
Debt Securities, Available-for-sale, Unrealized Loss Position		27
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss		$ 2