Investments - Schedule of Available-for-Sale Securities Whose Value is Below Amortized Cost (Details) $ in Millions	Jun. 30, 2025 USD ($) security	Dec. 31, 2024 USD ($) security
Fair Value
Nine months or greater, but less than twelve months	$ 11,757	$ 21,106
Twelve months or greater	40,374	35,528
Total	52,131	56,634
Gross Unrealized Losses
Nine months or greater, but less than twelve months	833	1,524
Twelve months or greater	6,145	6,262
Total	$ 6,978	$ 7,786
Number of Securities
Total | security	6,022	6,645
Fair Value Decline, Greater Than 20%
Fair Value
Less than six months	$ 1,797	$ 5,209
Six months or greater, but less than nine months	1,163	365
Nine months or greater, but less than twelve months	1,455	71
Twelve months or greater	4,513	4,305
Total	8,928	9,950
Gross Unrealized Losses
Less than six months	557	1,556
Six months or greater, but less than nine months	353	195
Nine months or greater, but less than twelve months	478	28
Twelve months or greater	2,217	2,142
Total	$ 3,605	$ 3,921
Number of Securities
Less than six months | security	352	780
Six months or greater, but less than nine months | security	239	209
Nine months or greater, but less than twelve months | security	297	36
Twelve months or greater | security	789	734
Total | security	1,677	1,759