Investments - Schedule of Available-for-Sale Securities Whose Value is Below Amortized Cost (Details) $ in Millions	Dec. 31, 2023 USD ($) security	Dec. 31, 2022 USD ($) security
Fair Value
Nine months or greater, but less than twelve months	$ 16,851	$ 69,198
Twelve months or greater	43,082	11,105
Total	59,933	80,303
Gross Unrealized Losses
Nine months or greater, but less than twelve months	1,999	10,013
Twelve months or greater	4,967	2,486
Total	$ 6,966	$ 12,499
Number of Securities
Total | security	7,167,000,000	8,106,000,000
Fair Value Decline, Greater Than 20%
Fair Value
Less than six months	$ 2,480	$ 10,895
Six months or greater, but less than nine months	321	4,256
Nine months or greater, but less than twelve months	321	362
Twelve months or greater	3,485	2
Total	6,607	15,515
Gross Unrealized Losses
Less than six months	916	3,514
Six months or greater, but less than nine months	90	2,150
Nine months or greater, but less than twelve months	106	243
Twelve months or greater	1,336	0
Total	$ 2,448	$ 5,907
Number of Securities
Less than six months | security	529,000,000	1,489,000,000
Six months or greater, but less than nine months | security	79,000,000	640,000,000
Nine months or greater, but less than twelve months | security	87,000,000	73,000,000
Twelve months or greater | security	704,000,000	15,000,000
Total | security	1,399,000,000	2,217,000,000