Investments - Unrealized Capital Losses (Details) $ in Millions	Mar. 31, 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	1,754
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 2,192	$ 2,628
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 558
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | securities	4,031	4,222
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | securities	2,277	1,069
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 8,404	$ 3,143
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	8,921
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	1,634	861
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	$ 17,325	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]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year | securities	69
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 33
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	10
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 19	$ 31
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 1
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | securities	20	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	$ 83	$ 2
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	58
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	18	1
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	$ 141	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	196
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 68	$ 92
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 31
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | securities	279	292
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | securities	83	16
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 139	$ 15
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	419
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	37	7
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	$ 558	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	474
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 832	$ 1,032
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 175
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | securities	1,163	1,261
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | securities	689	360
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 2,333	$ 998
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	2,522
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	657	419
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	$ 4,855	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	184
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 273	$ 328
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 89
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | securities	330	344
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | securities	146	32
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 1,242	$ 331
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	1,734
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	184	64
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	$ 2,976	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	195
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 259	$ 317
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 56
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | securities	413	441
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | securities	218	93
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 777	$ 298
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	905
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	203	116
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	$ 1,682	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	130
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 139	$ 184
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 60
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | securities	194	206
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | securities	64	6
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 643	$ 52
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	1,492
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	79	11
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	$ 2,135	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	280
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 131	$ 153
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 28
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | securities	618	656
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | securities	338	215
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 588	$ 328
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	501
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	103	75
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	$ 1,089	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	175
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 371	$ 379
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 102
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | securities	566	562
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | securities	391	189
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 1,594	$ 759
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	950
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	269	127
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	$ 2,544	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	110
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 98	$ 109
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	446	436
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | securities	336	155
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 988	$ 360
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	340
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	82	41
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	$ 1,328	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	0
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 2
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	2
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	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	2
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	$ 17
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