Investments - Schedule of Available-for-Sale Securities Whose Value is Below Amortized Cost (Details) $ in Millions	Mar. 31, 2026 USD ($) security	Dec. 31, 2025 USD ($) security
Fair Value
Nine months or greater, but less than twelve months	$ 26,462	$ 13,038
Twelve months or greater	34,471	36,491
Total	60,933	49,529
Gross Unrealized Losses
Nine months or greater, but less than twelve months	1,556	1,325
Twelve months or greater	5,437	4,939
Total	$ 6,993	$ 6,264
Number of Securities
Total | security	7,002	5,738
Fair Value Decline, Greater Than 20%
Fair Value
Less than six months	$ 3,501	$ 2,318
Six months or greater, but less than nine months	904	337
Nine months or greater, but less than twelve months	298	302
Twelve months or greater	4,733	4,985
Total	9,436	7,942
Gross Unrealized Losses
Less than six months	1,040	829
Six months or greater, but less than nine months	449	159
Nine months or greater, but less than twelve months	161	119
Twelve months or greater	2,180	2,089
Total	$ 3,830	$ 3,196
Number of Securities
Less than six months | security	567	441
Six months or greater, but less than nine months | security	209	60
Nine months or greater, but less than twelve months | security	56	99
Twelve months or greater | security	858	889
Total | security	1,690	1,489