Investments - Schedule of Available-for-Sale Securities Whose Value is Below Amortized Cost (Details) $ in Millions	Dec. 31, 2024 USD ($) security	Dec. 31, 2023 USD ($) security
Fair Value
Nine months or greater, but less than twelve months	$ 21,106	$ 16,851
Twelve months or greater	35,528	43,082
Total	56,634	59,933
Gross Unrealized Losses
Nine months or greater, but less than twelve months	1,524	1,999
Twelve months or greater	6,262	4,967
Total	$ 7,786	$ 6,966
Number of Securities
Total | security	6,645,000,000	7,167,000,000
Fair Value Decline, Greater Than 20%
Fair Value
Less than six months	$ 5,209	$ 2,480
Six months or greater, but less than nine months	365	321
Nine months or greater, but less than twelve months	71	321
Twelve months or greater	4,305	3,485
Total	9,950	6,607
Gross Unrealized Losses
Less than six months	1,556	916
Six months or greater, but less than nine months	195	90
Nine months or greater, but less than twelve months	28	106
Twelve months or greater	2,142	1,336
Total	$ 3,921	$ 2,448
Number of Securities
Less than six months | security	780,000,000	529,000,000
Six months or greater, but less than nine months | security	209,000,000	79,000,000
Nine months or greater, but less than twelve months | security	36,000,000	87,000,000
Twelve months or greater | security	734,000,000	704,000,000
Total | security	1,759,000,000	1,399,000,000