Investments - Schedule of Available-for-Sale Securities Whose Value is Below Amortized Cost (Details) $ in Millions	Mar. 31, 2025 USD ($) security	Dec. 31, 2024 USD ($) security
Fair Value
Nine months or greater, but less than twelve months	$ 20,346	$ 21,106
Twelve months or greater	34,921	35,528
Total	55,267	56,634
Gross Unrealized Losses
Nine months or greater, but less than twelve months	1,438	1,524
Twelve months or greater	5,834	6,262
Total	$ 7,272	$ 7,786
Number of Securities
Total | security	6,492	6,645,000,000
Fair Value Decline, Greater Than 20%
Fair Value
Less than six months	$ 2,967	$ 5,209
Six months or greater, but less than nine months	1,528	365
Nine months or greater, but less than twelve months	363	71
Twelve months or greater	4,245	4,305
Total	9,103	9,950
Gross Unrealized Losses
Less than six months	872	1,556
Six months or greater, but less than nine months	495	195
Nine months or greater, but less than twelve months	184	28
Twelve months or greater	2,074	2,142
Total	$ 3,625	$ 3,921
Number of Securities
Less than six months | security	502	780,000,000
Six months or greater, but less than nine months | security	317	209,000,000
Nine months or greater, but less than twelve months | security	201	36,000,000
Twelve months or greater | security	728	734,000,000
Total | security	1,748	1,759,000,000