Fair Value Measurement - Carrying Value and Estimated Fair Value (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Financial assets
Cash and due from banks	$ 23,873	$ 20,490	$ 27,831	$ 39,771
Deposits with banks	365,762	340,015
Federal funds sold and securities purchased under resale agreements	229,967	212,575
Securities, held-to-maturity	50,889	50,587
Loans, net of allowance for loan losses	2,230	2,861
Financial liabilities
Commercial paper	11,738	15,562
Beneficial interests issued by consolidated VIEs	39,047	41,879
Carrying value
Financial assets
Cash and due from banks	23,900	20,500
Deposits with banks	365,800	340,000
Accrued interest and accounts receivable	52,300	46,600
Federal funds sold and securities purchased under resale agreements	208,500	189,500
Securities borrowed	96,400	98,300
Securities, held-to-maturity	50,200	49,100
Loans, net of allowance for loan losses	878,800	820,800
Other	71,400	66,000
Financial liabilities
Deposits	1,361,300	1,267,200
Federal funds purchased and securities loaned or sold under repurchase agreements	165,000	149,200
Commercial paper	11,700	15,600
Other borrowed funds	13,600	11,200
Accounts payable and other liabilities	148,000	144,600
Beneficial interests issued by consolidated VIEs	38,900	41,100
Long-term debt and junior subordinated deferrable interest debentures	257,500	255,600
Wholesale lending-related commitments	1,100	800
Fair value
Financial assets
Cash and due from banks	23,900	20,500
Deposits with banks	365,800	340,000
Accrued interest and accounts receivable	52,300	46,600
Federal funds sold and securities purchased under resale agreements	208,500	189,500
Securities borrowed	96,400	98,300
Securities, held-to-maturity	50,900	50,600
Loans, net of allowance for loan losses	875,100	828,100
Other	75,200	70,700
Financial liabilities
Deposits	1,361,300	1,267,300
Federal funds purchased and securities loaned or sold under repurchase agreements	165,000	149,200
Commercial paper	11,700	15,600
Other borrowed funds	13,600	11,200
Accounts payable and other liabilities	148,200	144,500
Beneficial interests issued by consolidated VIEs	38,900	41,100
Long-term debt and junior subordinated deferrable interest debentures	262,000	261,700
Wholesale lending-related commitments	2,100	3,000
Fair value | Level 1
Financial assets
Cash and due from banks	23,900	20,500
Deposits with banks	362,000	335,900
Accrued interest and accounts receivable	0	0
Federal funds sold and securities purchased under resale agreements	0	0
Securities borrowed	0	0
Securities, held-to-maturity	0	0
Loans, net of allowance for loan losses	0	0
Other	100	100
Financial liabilities
Deposits	0	0
Federal funds purchased and securities loaned or sold under repurchase agreements	0	0
Commercial paper	0	0
Other borrowed funds	0	0
Accounts payable and other liabilities	0	0
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
Fair value | Level 2
Financial assets
Cash and due from banks	0	0
Deposits with banks	3,800	4,100
Accrued interest and accounts receivable	52,200	46,400
Federal funds sold and securities purchased under resale agreements	208,300	189,500
Securities borrowed	96,400	98,300
Securities, held-to-maturity	50,900	50,600
Loans, net of allowance for loan losses	24,100	25,400
Other	60,800	56,300
Financial liabilities
Deposits	1,361,300	1,266,100
Federal funds purchased and securities loaned or sold under repurchase agreements	165,000	149,200
Commercial paper	11,700	15,600
Other borrowed funds	13,600	11,200
Accounts payable and other liabilities	144,800	141,700
Beneficial interests issued by consolidated VIEs	38,900	40,200
Long-term debt and junior subordinated deferrable interest debentures	260,000	257,400
Wholesale lending-related commitments	0	0
Fair value | Level 3
Financial assets
Cash and due from banks	0	0
Deposits with banks	0	0
Accrued interest and accounts receivable	100	200
Federal funds sold and securities purchased under resale agreements	200	0
Securities borrowed	0	0
Securities, held-to-maturity	0	0
Loans, net of allowance for loan losses	851,000	802,700
Other	14,300	14,300
Financial liabilities
Deposits	0	1,200
Federal funds purchased and securities loaned or sold under repurchase agreements	0	0
Commercial paper	0	0
Other borrowed funds	0	0
Accounts payable and other liabilities	3,400	2,800
Beneficial interests issued by consolidated VIEs	0	900
Long-term debt and junior subordinated deferrable interest debentures	2,000	4,300
Wholesale lending-related commitments	$ 2,100	$ 3,000