Investments - Unrealized Capital Losses (Details) $ in Millions	Jun. 30, 2023 USD ($) securities	Dec. 31, 2022 USD ($) securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions | securities	946
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 2,397	$ 2,628
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 228
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | securities	4,046	4,222
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | securities	3,100	1,069
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 12,400	$ 3,143
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	4,685
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	2,169	861
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	$ 17,085	18,531
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Fair Value		15,388
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Accumulated Loss		$ 1,767
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Number of Securities | securities		3,153
Fair value decline below amortized cost greater than 20%
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | securities	543
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 618
U.S. Treasuries
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions | securities	23
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 23	$ 31
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 3
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | securities	33	21
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | securities	10	3
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 81	$ 2
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	120
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	20	1
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	$ 201	225
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Fair Value		223
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Accumulated Loss		$ 30
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Number of Securities | securities		18
State, municipalities and political subdivisions
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions | securities	76
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 76	$ 92
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 8
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | securities	288	292
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | securities	212	16
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 411	$ 15
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	155
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	68	7
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	$ 566	560
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Fair Value		545
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Accumulated Loss		$ 85
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Number of Securities | securities		276
U.S. corporate public securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions | securities	278
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 902	$ 1,032
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 72
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | securities	1,191	1,261
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | securities	913	360
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 3,470	$ 998
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	1,345
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	830	419
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	$ 4,815	5,288
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Fair Value		4,290
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Accumulated Loss		$ 613
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Number of Securities | securities		901
U.S. corporate private securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions | securities	95
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 325	$ 328
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 44
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | securities	333	344
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | securities	238	32
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 2,049	$ 331
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	949
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	281	64
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	$ 2,998	3,150
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Fair Value		2,819
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Accumulated Loss		$ 264
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Number of Securities | securities		312
Foreign corporate public securities and foreign governments
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions | securities	94
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 266	$ 317
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 16
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | securities	411	441
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | securities	317	93
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 1,188	$ 298
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	459
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	250	116
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	$ 1,647	1,807
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Fair Value		1,509
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Accumulated Loss		$ 201
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Number of Securities | securities		348
Foreign corporate private securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions | securities	66
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 158	$ 184
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 27
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | securities	193	206
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | securities	127	6
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 1,265	$ 52
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	814
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	131	11
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	$ 2,079	2,255
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Fair Value		2,203
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Accumulated Loss		$ 173
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Number of Securities | securities		200
Residential mortgage-backed
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions | securities	205
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 141	$ 153
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 17
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | securities	621	656
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | securities	416	215
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 712	$ 328
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	355
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	124	75
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	$ 1,067	1,393
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Fair Value		1,065
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Accumulated Loss		$ 78
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Number of Securities | securities		441
Commercial mortgage-backed
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions | securities	72
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 418	$ 379
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 36
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | securities	547	562
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | securities	475	189
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 2,062	$ 759
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	355
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	382	127
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	$ 2,417	2,551
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Fair Value		1,792
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Accumulated Loss		$ 252
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Number of Securities | securities		373
Other asset-backed securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions | securities	36
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 85	$ 109
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 5
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | securities	426	436
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | securities	390	155
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 1,145	$ 360
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	120
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	80	41
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	$ 1,265	1,272
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Fair Value		912
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Accumulated Loss		$ 68
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Number of Securities | securities		281
US Government Corporations and Agencies Securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions | securities	1
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 3
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 0
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | securities	3
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | securities	2
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 17
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	13
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	3
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	$ 30
US Treasury and Government
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss		$ 3
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | securities		3
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | securities		0
Debt Securities, Available-for-sale, Unrealized Loss Position		$ 0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer		0
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value		30
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Fair Value		30
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Accumulated Loss		$ 3
Debt Securities, Available-for-sale, Including Securities Pledged, Continuous Unrealized Loss Position Twelve Months or Less, Number of Securities | securities		3