Investment Securities - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Investment Holdings [Line Items]
Accrued interest receivables on investment securities		$ 146	$ 131
Impairment losses		5	1	$ 19
Securities with a fair value, pledged as collateral		25,200	11,000
Unrealized losses		5,379	6,046
Subsequent Event
Investment Holdings [Line Items]
Transfer from available-for-sale to held-to-maturity	$ 12,600
Pretax, unrealized losses	$ 994
Non-rated Securities
Investment Holdings [Line Items]
Unrealized losses		$ 45	$ 42