Fair Value Measurement - Carrying Value and Estimated Fair Value (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Financial assets
Cash and due from banks	$ 21,946	$ 22,324
Deposits with banks	280,658	256,469
Federal funds sold and securities purchased under resale agreements	299,140	321,588
Investment securities, held-to-maturity	31,456	31,458
Loans, net of allowance for loan losses	3,719	3,151
Financial liabilities
Beneficial interests issued by consolidated VIEs	25,955	20,241
Carrying value
Financial assets
Cash and due from banks	21,900	22,300
Deposits with banks	280,700	256,500
Accrued interest and accounts receivable	71,200	72,000
Federal funds sold and securities purchased under resale agreements	285,200	308,400
Securities borrowed	117,500	106,900
Investment securities, held-to-maturity	30,800	31,400
Loans, net of allowance for loan losses	939,000	968,000
Other	56,500	60,500
Financial liabilities
Deposits	1,461,600	1,447,400
Federal funds purchased and securities loaned or sold under repurchase agreements	221,700	181,400
Short-term borrowings	64,100	62,100
Accounts payable and other liabilities	176,600	160,600
Beneficial interests issued by consolidated VIEs	25,900	20,200
Long-term debt and junior subordinated deferrable interest debentures	229,400	227,100
Wholesale lending-related commitments	1,000	1,000
Total estimated fair value
Financial assets
Cash and due from banks	21,900	22,300
Deposits with banks	280,700	256,500
Accrued interest and accounts receivable	71,200	72,000
Federal funds sold and securities purchased under resale agreements	285,200	308,400
Securities borrowed	117,500	106,900
Investment securities, held-to-maturity	31,500	31,500
Loans, net of allowance for loan losses	947,300	970,000
Other	56,600	60,600
Financial liabilities
Deposits	1,461,700	1,447,500
Federal funds purchased and securities loaned or sold under repurchase agreements	221,700	181,400
Short-term borrowings	64,100	62,100
Accounts payable and other liabilities	176,300	160,200
Beneficial interests issued by consolidated VIEs	25,900	20,200
Long-term debt and junior subordinated deferrable interest debentures	233,200	227,900
Wholesale lending-related commitments	1,800	1,900
Total estimated fair value | Level 1
Financial assets
Cash and due from banks	21,900	22,300
Deposits with banks	280,700	256,500
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	0	0
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	100	200
Beneficial interests issued by consolidated VIEs	0	0
Long-term debt and junior subordinated deferrable interest debentures	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	71,100	71,900
Federal funds sold and securities purchased under resale agreements	285,200	308,400
Securities borrowed	117,500	106,900
Investment securities, held-to-maturity	31,500	31,500
Loans, net of allowance for loan losses	229,800	241,500
Other	55,700	59,600
Financial liabilities
Deposits	1,461,700	1,447,500
Federal funds purchased and securities loaned or sold under repurchase agreements	221,700	181,400
Short-term borrowings	64,100	62,100
Accounts payable and other liabilities	173,000	157,000
Beneficial interests issued by consolidated VIEs	25,900	20,200
Long-term debt and junior subordinated deferrable interest debentures	229,900	224,600
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	717,500	728,500
Other	900	1,000
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	3,200	3,000
Beneficial interests issued by consolidated VIEs	0	0
Long-term debt and junior subordinated deferrable interest debentures	3,300	3,300
Wholesale lending-related commitments	$ 1,800	$ 1,900