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	$ 29,293	$ 30,166
Twelve months or greater	35,734	36,345
Total	65,027	66,511
Gross Unrealized Losses
Nine months or greater, but less than twelve months	4,217	4,537
Twelve months or greater	6,046	6,468
Total	$ 10,263	$ 11,005
Number of Securities
Total | security	6,835	6,985,000,000
Fair Value Decline, Greater Than 20%
Fair Value
Less than six months	$ 3,053	$ 5,405
Six months or greater, but less than nine months	1,600	371
Nine months or greater, but less than twelve months	369	71
Twelve months or greater	4,381	4,440
Total	9,403	10,287
Gross Unrealized Losses
Less than six months	900	1,621
Six months or greater, but less than nine months	518	198
Nine months or greater, but less than twelve months	187	28
Twelve months or greater	2,149	2,218
Total	$ 3,754	$ 4,065
Number of Securities
Less than six months | security	522	799,000,000
Six months or greater, but less than nine months | security	324	216,000,000
Nine months or greater, but less than twelve months | security	208	37,000,000
Twelve months or greater | security	737	741,000,000
Total | security	1,791	1,793,000,000