Fair Value, Estimates for Financial Instruments Excluding those Recorded at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	Sep. 30, 2015		Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2013
Financial assets
Cash and due from banks	$ 17,395		$ 19,571	$ 18,032	$ 19,919
Federal funds sold, securities purchased under resale agreements and other short-term investments	254,811		258,429
Held-to-maturity securities	78,668		55,483
Mortgages held for sale	21,840	[1]	19,536
Loans held for sale	430	[1]	722
Loans	903,233	[1]	862,551
Nonmarketable equity investments (cost method)	6,786		7,033
Financial liabilities
Deposits	1,202,179		1,168,310
Short-term borrowings	88,069		63,518
Long-Term Debt	185,274		183,943
Capital Lease Obligations	8		9
Carrying value [Member]
Financial assets
Cash and due from banks	17,395		19,571
Federal funds sold, securities purchased under resale agreements and other short-term investments	254,811		258,429
Held-to-maturity securities	78,668		55,483
Mortgages held for sale	4,213		3,971
Loans held for sale	430		721
Loans	874,085		832,671
Nonmarketable equity investments (cost method)	6,786		7,033
Financial liabilities
Deposits	1,202,179		1,196,663
Short-term borrowings	88,069		63,518
Long-Term Debt	185,266		183,934
Estimated fair value [Member]
Financial assets
Cash and due from banks	17,395		19,571
Federal funds sold, securities purchased under resale agreements and other short-term investments	254,811		258,429
Held-to-maturity securities	80,119		56,359
Mortgages held for sale	4,215		3,973
Loans held for sale	438		739
Loans	887,706		844,838
Nonmarketable equity investments (cost method)	7,916		8,377
Financial liabilities
Deposits	1,202,359		1,168,411
Short-term borrowings	88,069		63,518
Long-Term Debt	184,702		185,475
Loan Commitments And Standby, Commercial And Similar Letters of Credit	992		945
Estimated fair value [Member] | Fair Value, Inputs, Level 1 [Member]
Financial assets
Cash and due from banks	17,395		19,571
Federal funds sold, securities purchased under resale agreements and other short-term investments	17,668		8,991
Held-to-maturity securities	45,974		41,548
Mortgages held for sale	0		0
Loans held for sale	0		0
Loans	0		0
Nonmarketable equity investments (cost method)	0		0
Financial liabilities
Deposits	0		0
Short-term borrowings	0		0
Long-Term Debt	0		0
Estimated fair value [Member] | Fair Value, Inputs, Level 2 [Member]
Financial assets
Cash and due from banks	0		0
Federal funds sold, securities purchased under resale agreements and other short-term investments	236,966		249,438
Held-to-maturity securities	30,533		9,021
Mortgages held for sale	3,269		2,875
Loans held for sale	438		739
Loans	60,970		60,052
Nonmarketable equity investments (cost method)	0		0
Financial liabilities
Deposits	1,171,938		1,132,845
Short-term borrowings	88,069		63,518
Long-Term Debt	174,284		174,996
Estimated fair value [Member] | Fair Value, Inputs, Level 3 [Member]
Financial assets
Cash and due from banks	0		0
Federal funds sold, securities purchased under resale agreements and other short-term investments	177		0
Held-to-maturity securities	3,612		5,790
Mortgages held for sale	946		1,098
Loans held for sale	0		0
Loans	826,736		784,786
Nonmarketable equity investments (cost method)	7,916		8,377
Financial liabilities
Deposits	30,421		35,566
Short-term borrowings	0		0
Long-Term Debt	10,418		10,479
Finance Leases Financing Receivable [Member]
Financial assets
Loans	$ 12,142		$ 12,307

[1] Parenthetical amounts represent assets and liabilities for which we have elected the fair value option.