Investment Securities - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Jan. 31, 2024	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Summary of Investment Holdings [Line Items]
Accrued interest receivables on investment securities		$ 162		$ 146
Transfer of available-for-sale securities to held-to-maturity	$ 12,600
OCI, available-for-sale debt securities transferred to held-to-maturity, pretax unrealized losses	$ 994
Impairment losses		5	$ 0
Securities with a fair value, pledged as collateral		31,900		25,200
Unrealized losses		4,614		5,379
Available-for-sale debt securities transferred to held-to-maturity securities
Summary of Investment Holdings [Line Items]
AOCI offset, unamortized portion of unrealized losses on securities		962
Non-rated Securities
Summary of Investment Holdings [Line Items]
Unrealized losses		36		45
Other Debt Obligations [Member]
Summary of Investment Holdings [Line Items]
Federal Home Loan Bank Stock		301		224
FRB, restricted stock holdings		496		496
DTCC, restricted stock holdings		$ 3		$ 2