Fair Value Measurement - Carrying Value and Estimated Fair Value (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Financial assets
Cash and due from banks	$ 25,397	$ 24,874
Deposits with banks	685,675	502,735
Federal funds sold and securities purchased under resale agreements	272,481	296,284
Investment securities, held-to-maturity	217,710	205,472
Loans, net of allowance for loan losses	50,767	44,474
Financial liabilities
Beneficial interests issued by consolidated VIEs	15,671	17,578
Carrying value
Financial assets
Cash and due from banks	25,400	24,900
Deposits with banks	685,700	502,700
Accrued interest and accounts receivable	113,600	89,400
Federal funds sold and securities purchased under resale agreements	4,900	58,300
Securities borrowed	113,400	107,700
Investment securities, held-to-maturity	217,500	201,800
Loans, net of allowance for loan losses	937,500	940,100
Other	95,000	81,800
Financial liabilities
Deposits	2,264,000	2,129,800
Federal funds purchased and securities loaned or sold under repurchase agreements	106,200	59,500
Short-term borrowings	35,000	28,300
Accounts payable and other liabilities	205,900	186,600
Beneficial interests issued by consolidated VIEs	15,500	17,500
Long-term debt	203,700	204,800
Wholesale lending-related commitments	2,400	2,200
Total estimated fair value
Financial assets
Cash and due from banks	25,400	24,900
Deposits with banks	685,700	502,700
Accrued interest and accounts receivable	113,600	89,400
Federal funds sold and securities purchased under resale agreements	4,900	58,300
Securities borrowed	113,200	107,700
Investment securities, held-to-maturity	217,700	205,500
Loans, net of allowance for loan losses	959,400	966,500
Other	95,100	81,900
Financial liabilities
Deposits	2,264,000	2,128,900
Federal funds purchased and securities loaned or sold under repurchase agreements	106,200	59,500
Short-term borrowings	35,000	28,300
Accounts payable and other liabilities	205,500	186,200
Beneficial interests issued by consolidated VIEs	15,500	17,600
Long-term debt	211,100	212,400
Wholesale lending-related commitments	2,800	2,100
Total estimated fair value | Level 1
Financial assets
Cash and due from banks	25,400	24,900
Deposits with banks	685,700	502,700
Accrued interest and accounts receivable	0	0
Federal funds sold and securities purchased under resale agreements	0	0
Securities borrowed	0	0
Investment securities, held-to-maturity	74,500	53,200
Loans, net of allowance for loan losses	0	0
Other	0	0
Financial liabilities
Deposits	0	0
Federal funds purchased and securities loaned or sold under repurchase agreements	0	0
Short-term borrowings	0	0
Accounts payable and other liabilities	0	0
Beneficial interests issued by consolidated VIEs	0	0
Long-term debt	0	0
Wholesale lending-related commitments	0	0
Total estimated fair value | Level 2
Financial assets
Cash and due from banks	0	0
Deposits with banks	0	0
Accrued interest and accounts receivable	113,500	89,300
Federal funds sold and securities purchased under resale agreements	4,900	58,300
Securities borrowed	113,200	107,700
Investment securities, held-to-maturity	143,200	152,300
Loans, net of allowance for loan losses	206,700	210,900
Other	93,200	80,000
Financial liabilities
Deposits	2,264,000	2,128,900
Federal funds purchased and securities loaned or sold under repurchase agreements	106,200	59,500
Short-term borrowings	35,000	28,300
Accounts payable and other liabilities	201,600	181,900
Beneficial interests issued by consolidated VIEs	15,500	17,600
Long-term debt	207,800	209,200
Wholesale lending-related commitments	0	0
Total estimated fair value | Level 3
Financial assets
Cash and due from banks	0	0
Deposits with banks	0	0
Accrued interest and accounts receivable	100	100
Federal funds sold and securities purchased under resale agreements	0	0
Securities borrowed	0	0
Investment securities, held-to-maturity	0	0
Loans, net of allowance for loan losses	752,700	755,600
Other	1,900	1,900
Financial liabilities
Deposits	0	0
Federal funds purchased and securities loaned or sold under repurchase agreements	0	0
Short-term borrowings	0	0
Accounts payable and other liabilities	3,900	4,300
Beneficial interests issued by consolidated VIEs	0	0
Long-term debt	3,300	3,200
Wholesale lending-related commitments	$ 2,800	$ 2,100