Fair Value Measurement - Carrying Value and Estimated Fair Value (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Financial assets
Cash and due from banks	$ 18,212	$ 20,490	$ 22,821	$ 27,831
Deposits with banks	360,196	340,015
Federal funds sold and securities purchased under resale agreements	223,220	212,575
Securities, held-to-maturity	50,168	50,587
Financial liabilities
Commercial paper	17,490	15,562
Beneficial interests issued by consolidated VIEs	38,673	41,879
Carrying value
Financial assets
Cash and due from banks	18,200	20,500
Deposits with banks	360,200	340,000
Accrued interest and accounts receivable	57,600	46,600
Federal funds sold and securities purchased under resale agreements	199,100	189,500
Securities borrowed	102,900	98,300
Securities, held-to-maturity	47,900	49,100
Loans, net of allowance for loan losses	831,400	820,800
Other	71,400	66,000
Financial liabilities
Deposits	1,309,800	1,267,200
Federal funds purchased and securities loaned or sold under repurchase agreements	157,600	149,200
Commercial paper	17,500	15,600
Other borrowed funds	10,100	11,200
Accounts payable and other liabilities	148,400	144,600
Beneficial interests issued by consolidated VIEs	38,000	41,100
Long-term debt and junior subordinated deferrable interest debentures	255,600	255,600
Wholesale lending-related commitments	1,000	800
Estimated fair value hierarchy
Financial assets
Cash and due from banks	18,200	20,500
Deposits with banks	360,200	340,000
Accrued interest and accounts receivable	57,600	46,600
Federal funds sold and securities purchased under resale agreements	199,100	189,500
Securities borrowed	102,900	98,300
Securities, held-to-maturity	50,200	50,600
Loans, net of allowance for loan losses	837,700	828,100
Other	76,000	70,700
Financial liabilities
Deposits	1,309,900	1,267,300
Federal funds purchased and securities loaned or sold under repurchase agreements	157,500	149,200
Commercial paper	17,500	15,600
Other borrowed funds	10,100	11,200
Accounts payable and other liabilities	148,200	144,500
Beneficial interests issued by consolidated VIEs	38,000	41,100
Long-term debt and junior subordinated deferrable interest debentures	264,100	261,700
Wholesale lending-related commitments	2,900	3,000
Estimated fair value hierarchy | Level 1
Financial assets
Cash and due from banks	18,200	20,500
Deposits with banks	354,100	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
Estimated fair value hierarchy | Level 2
Financial assets
Cash and due from banks	0	0
Deposits with banks	6,100	4,100
Accrued interest and accounts receivable	57,400	46,400
Federal funds sold and securities purchased under resale agreements	198,900	189,500
Securities borrowed	102,900	98,300
Securities, held-to-maturity	50,200	50,600
Loans, net of allowance for loan losses	24,500	25,400
Other	61,600	56,300
Financial liabilities
Deposits	1,308,300	1,266,100
Federal funds purchased and securities loaned or sold under repurchase agreements	156,800	149,200
Commercial paper	17,500	15,600
Other borrowed funds	10,100	11,200
Accounts payable and other liabilities	145,600	141,700
Beneficial interests issued by consolidated VIEs	37,200	40,200
Long-term debt and junior subordinated deferrable interest debentures	259,800	257,400
Wholesale lending-related commitments	0	0
Estimated fair value hierarchy | Level 3
Financial assets
Cash and due from banks	0	0
Deposits with banks	0	0
Accrued interest and accounts receivable	200	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	813,200	802,700
Other	14,300	14,300
Financial liabilities
Deposits	1,600	1,200
Federal funds purchased and securities loaned or sold under repurchase agreements	700	0
Commercial paper	0	0
Other borrowed funds	0	0
Accounts payable and other liabilities	2,600	2,800
Beneficial interests issued by consolidated VIEs	800	900
Long-term debt and junior subordinated deferrable interest debentures	4,300	4,300
Wholesale lending-related commitments	$ 2,900	$ 3,000