Investments - Schedule of Available-for-Sale Securities Whose Value is Below Amortized Cost (Details) $ in Millions	Jun. 30, 2024 USD ($) security	Dec. 31, 2023 USD ($) security
Fair Value
Nine months or greater, but less than twelve months	$ 36,227	$ 17,427
Twelve months or greater	34,177	44,508
Total	70,404	61,935
Gross Unrealized Losses
Nine months or greater, but less than twelve months	6,009	3,526
Twelve months or greater	5,213	6,241
Total	$ 11,222	$ 9,767
Number of Securities
Total | security	7,467	7,605
Fair Value Decline, Greater Than 20%
Fair Value
Less than six months	$ 3,536	$ 2,492
Six months or greater, but less than nine months	2,352	343
Nine months or greater, but less than twelve months	378	336
Twelve months or greater	3,321	4,094
Total	9,587	7,265
Gross Unrealized Losses
Less than six months	1,067	927
Six months or greater, but less than nine months	974	96
Nine months or greater, but less than twelve months	156	109
Twelve months or greater	1,451	2,922
Total	$ 3,648	$ 4,054
Number of Securities
Less than six months | security	690	533
Six months or greater, but less than nine months | security	496	79
Nine months or greater, but less than twelve months | security	124	90
Twelve months or greater | security	653	997
Total | security	1,963	1,699