Investments - Schedule of Available-for-Sale Securities Whose Value is Below Amortized Cost (Details) $ in Millions	Sep. 30, 2025 USD ($) security	Dec. 31, 2024 USD ($) security
Fair Value
Nine months or greater, but less than twelve months	$ 9,887	$ 21,106
Twelve months or greater	38,455	35,528
Total	48,342	56,634
Gross Unrealized Losses
Nine months or greater, but less than twelve months	1,048	1,524
Twelve months or greater	5,183	6,262
Total	$ 6,231	$ 7,786
Number of Securities
Total | security	5,628	6,645
Fair Value Decline, Greater Than 20%
Fair Value
Less than six months	$ 1,155	$ 5,209
Six months or greater, but less than nine months	458	365
Nine months or greater, but less than twelve months	709	71
Twelve months or greater	5,083	4,305
Total	7,405	9,950
Gross Unrealized Losses
Less than six months	514	1,556
Six months or greater, but less than nine months	158	195
Nine months or greater, but less than twelve months	205	28
Twelve months or greater	2,125	2,142
Total	$ 3,002	$ 3,921
Number of Securities
Less than six months | security	179	780
Six months or greater, but less than nine months | security	133	209
Nine months or greater, but less than twelve months | security	176	36
Twelve months or greater | security	898	734
Total | security	1,386	1,759