Fair Value Measurement - Carrying Value and Estimated Fair Value (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Financial assets
Cash and due from banks	$ 20,490	$ 27,831	$ 39,771	$ 53,723
Deposits with banks	340,015	484,477
Federal funds sold and securities purchased under resale agreements	212,575	215,803
Securities, held-to-maturity	50,587	51,154
Financial liabilities
Commercial paper	15,562	66,344
Beneficial interests issued by consolidated VIEs	41,879	52,320
Carrying value
Financial assets
Cash and due from banks	20,500	27,800
Deposits with banks	340,000	484,500
Accrued interest and accounts receivable	46,600	70,100
Federal funds sold and securities purchased under resale agreements	189,500	187,200
Securities borrowed	98,300	109,400
Securities, held-to-maturity	49,100	49,300
Loans, net of allowance for loan losses	820,800	740,500
Other	66,000	64,700
Financial liabilities
Deposits	1,267,200	1,354,600
Federal funds purchased and securities loaned or sold under repurchase agreements	149,200	189,100
Commercial paper	15,600	66,300
Other borrowed funds	11,200	15,500
Accounts payable and other liabilities	144,600	172,600
Beneficial interests issued by consolidated VIEs	41,100	50,200
Long-term debt and junior subordinated deferrable interest debentures	255,600	246,200
Wholesale lending-related commitments	800	600
Estimate of Fair Value
Financial assets
Cash and due from banks	20,500	27,800
Deposits with banks	340,000	484,500
Accrued interest and accounts receivable	46,600	70,100
Federal funds sold and securities purchased under resale agreements	189,500	187,200
Securities borrowed	98,300	109,400
Securities, held-to-maturity	50,600	51,200
Loans, net of allowance for loan losses	828,100	744,900
Other	70,700	69,000
Financial liabilities
Deposits	1,267,300	1,354,800
Federal funds purchased and securities loaned or sold under repurchase agreements	149,200	189,100
Commercial paper	15,600	66,300
Other borrowed funds	11,200	15,500
Accounts payable and other liabilities	144,500	172,500
Beneficial interests issued by consolidated VIEs	41,100	50,200
Long-term debt and junior subordinated deferrable interest debentures	261,700	255,000
Wholesale lending-related commitments	3,000	1,600
Estimate of Fair Value | Level 1
Financial assets
Cash and due from banks	20,500	27,800
Deposits with banks	335,900	480,400
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	0
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
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
Estimate of Fair Value | Level 2
Financial assets
Cash and due from banks	0	0
Deposits with banks	4,100	4,100
Accrued interest and accounts receivable	46,400	70,000
Federal funds sold and securities purchased under resale agreements	189,500	187,200
Securities borrowed	98,300	109,400
Securities, held-to-maturity	50,600	51,200
Loans, net of allowance for loan losses	25,400	21,800
Other	56,300	55,700
Financial liabilities
Deposits	1,266,100	1,353,600
Federal funds purchased and securities loaned or sold under repurchase agreements	149,200	189,100
Commercial paper	15,600	66,300
Other borrowed funds	11,200	15,500
Accounts payable and other liabilities	141,700	169,600
Beneficial interests issued by consolidated VIEs	40,200	48,200
Long-term debt and junior subordinated deferrable interest debentures	257,400	251,200
Wholesale lending-related commitments	0	0
Estimate of Fair Value | Level 3
Financial assets
Cash and due from banks	0	0
Deposits with banks	0	0
Accrued interest and accounts receivable	200	100
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	802,700	723,100
Other	14,300	13,300
Financial liabilities
Deposits	1,200	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	2,800	2,900
Beneficial interests issued by consolidated VIEs	900	2,000
Long-term debt and junior subordinated deferrable interest debentures	4,300	3,800
Wholesale lending-related commitments	$ 3,000	$ 1,600