Investments - Schedule of Available-for-Sale Securities Whose Value is Below Amortized Cost (Details) $ in Millions	Dec. 31, 2023 USD ($) security	Dec. 31, 2022 USD ($) security
Fair Value
Nine months or greater, but less than twelve months	$ 17,427	$ 71,770
Twelve months or greater	44,508	11,352
Total	61,935	83,122
Gross Unrealized Losses
Nine months or greater, but less than twelve months	3,526	10,425
Twelve months or greater	6,241	2,593
Total	$ 9,767	$ 13,018
Number of Securities
Total | security	7,605,000,000	8,175,000,000
Fair Value Decline, Greater Than 20%
Fair Value
Less than six months	$ 2,492	$ 11,351
Six months or greater, but less than nine months	343	4,411
Nine months or greater, but less than twelve months	336	447
Twelve months or greater	4,094	2
Total	7,265	16,211
Gross Unrealized Losses
Less than six months	927	3,659
Six months or greater, but less than nine months	96	2,226
Nine months or greater, but less than twelve months	109	302
Twelve months or greater	2,922	1
Total	$ 4,054	$ 6,188
Number of Securities
Less than six months | security	533,000,000	1,500,000,000
Six months or greater, but less than nine months | security	79,000,000	650,000,000
Nine months or greater, but less than twelve months | security	90,000,000	74,000,000
Twelve months or greater | security	997,000,000	15,000,000
Total | security	1,699,000,000	2,239,000,000