Investment Securities - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Jan. 31, 2024	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Summary of Investment Holdings [Line Items]
Accrued interest receivables on investment securities		$ 167		$ 167		$ 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		11	$ 1	21	$ 5
Securities with a fair value, pledged as collateral		31,400		31,400		25,200
Unrealized losses		3,370		3,370		5,379
Total gains (losses) recognized in income from available-for-sale debt and other securities, trading debt securities and equity securities		10	(7)	23	3
Commercial Banking Revenue and Wealth and Asset Management Revenue
Summary of Investment Holdings [Line Items]
Total gains (losses) recognized in income from available-for-sale debt and other securities, trading debt securities and equity securities		7	$ 2	9	$ 3
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		897		897
Non-rated Securities
Summary of Investment Holdings [Line Items]
Unrealized losses		29		29		45
Other Debt Obligations [Member]
Summary of Investment Holdings [Line Items]
Restricted stock holdings		275		275		224
FRB, restricted stock holdings		499		499		496
DTCC, restricted stock holdings		$ 3		$ 3		$ 2