Loans and Allowance for Credit Losses, Nonaccrual (Details) - USD ($) $ in Millions		Jun. 30, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	[1]	$ 957,423	$ 967,604
Total Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans		505,901	506,536
Commercial and Industrial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans		331,113	330,840
Commercial real estate mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans		130,277	132,491
Commercial Real Estate Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans		25,337	23,916
Commercial Lease Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans		19,174	19,289
Total Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans		451,522	461,068
Real estate 1-4 family first mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans		276,566	275,579
Real estate 1-4 family junior lien mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans		42,747	46,237
Automobile [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans		57,958	62,286
Other revolving credit and installment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans		38,946	40,266
Residential Real Estate [Member]
Nonaccrual Loans [Abstract]
Mortgage Loans in Process of Foreclosure, Amount		7,000	8,100
Government Guaranteed Mortgage Loans upon Foreclosure Receivable [Member]
Nonaccrual Loans [Abstract]
Mortgage Loans in Process of Foreclosure, Amount		4,100	4,800
Mortgages held for sale [Member] | Real estate 1-4 family first mortgage [Member]
Nonaccrual Loans [Abstract]
Nonaccrual loans		140	149
Loans Excluding Certain Loans Acquired In Transfer With Evidence Of Credit Deterioration [Member]
Nonaccrual Loans [Abstract]
Nonaccrual loans		9,056	10,384
Loans Excluding Certain Loans Acquired In Transfer With Evidence Of Credit Deterioration [Member] | Total Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans		505,638	505,859
Nonaccrual Loans [Abstract]
Nonaccrual loans		3,385	4,059
Loans Excluding Certain Loans Acquired In Transfer With Evidence Of Credit Deterioration [Member] | Commercial and Industrial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans		330,982	330,603
Nonaccrual Loans [Abstract]
Nonaccrual loans		2,632	3,216
Loans Excluding Certain Loans Acquired In Transfer With Evidence Of Credit Deterioration [Member] | Commercial real estate mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans		130,158	132,108
Nonaccrual Loans [Abstract]
Nonaccrual loans		630	685
Loans Excluding Certain Loans Acquired In Transfer With Evidence Of Credit Deterioration [Member] | Commercial Real Estate Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans		25,324	23,859
Nonaccrual Loans [Abstract]
Nonaccrual loans		34	43
Loans Excluding Certain Loans Acquired In Transfer With Evidence Of Credit Deterioration [Member] | Commercial Lease Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans		19,174	19,289
Nonaccrual Loans [Abstract]
Nonaccrual loans		89	115
Loans Excluding Certain Loans Acquired In Transfer With Evidence Of Credit Deterioration [Member] | Total Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans		437,512	445,014
Nonaccrual Loans [Abstract]
Nonaccrual loans		5,671	6,325
Loans Excluding Certain Loans Acquired In Transfer With Evidence Of Credit Deterioration [Member] | Real estate 1-4 family first mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans		262,587	259,561
Nonaccrual Loans [Abstract]
Nonaccrual loans		4,413	4,962
Loans Excluding Certain Loans Acquired In Transfer With Evidence Of Credit Deterioration [Member] | Real estate 1-4 family junior lien mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans		42,716	46,201
Nonaccrual Loans [Abstract]
Nonaccrual loans		1,095	1,206
Loans Excluding Certain Loans Acquired In Transfer With Evidence Of Credit Deterioration [Member] | Automobile [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans		57,958	62,286
Nonaccrual Loans [Abstract]
Nonaccrual loans		104	106
Loans Excluding Certain Loans Acquired In Transfer With Evidence Of Credit Deterioration [Member] | Other revolving credit and installment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans		38,946	40,266
Nonaccrual Loans [Abstract]
Nonaccrual loans		59	51
Criticized [Member] | Loans Excluding Certain Loans Acquired In Transfer With Evidence Of Credit Deterioration [Member] | Total Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans		25,409	29,593
Criticized [Member] | Loans Excluding Certain Loans Acquired In Transfer With Evidence Of Credit Deterioration [Member] | Commercial and Industrial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans		19,019	22,437
Criticized [Member] | Loans Excluding Certain Loans Acquired In Transfer With Evidence Of Credit Deterioration [Member] | Commercial real estate mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans		4,875	5,315
Criticized [Member] | Loans Excluding Certain Loans Acquired In Transfer With Evidence Of Credit Deterioration [Member] | Commercial Real Estate Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans		311	451
Criticized [Member] | Loans Excluding Certain Loans Acquired In Transfer With Evidence Of Credit Deterioration [Member] | Commercial Lease Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans		$ 1,204	$ 1,390

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