Loans and Allowance for Credit Losses, Loans by Delinquency Status, Commercial (Details) - USD ($) $ in Millions		Jun. 30, 2017	Dec. 31, 2016	Dec. 31, 2008
By delinquency status:
Loans	[1]	$ 957,423	$ 967,604
Total Commercial [Member]
By delinquency status:
Loans		505,901	506,536
Commercial and Industrial Loans [Member]
By delinquency status:
Loans		331,113	330,840
Commercial real estate mortgage [Member]
By delinquency status:
Loans		130,277	132,491
Commercial Real Estate Construction [Member]
By delinquency status:
Loans		25,337	23,916
Commercial Lease Financing Receivable [Member]
By delinquency status:
Loans		19,174	19,289
Loans Excluding Purchased Credit-Impaired Loans [Member]
By delinquency status:
Over 90 DPD and still accruing		9,716	11,858
Nonaccrual loans		9,056	10,384
Loans Excluding Purchased Credit-Impaired Loans [Member] | Total Commercial [Member]
By delinquency status:
Loans		505,638	505,859
Over 90 DPD and still accruing		54	64
Nonaccrual loans		3,385	4,059
Loans Excluding Purchased Credit-Impaired Loans [Member] | Commercial and Industrial Loans [Member]
By delinquency status:
Loans		330,982	330,603
Over 90 DPD and still accruing		42	28
Nonaccrual loans		2,632	3,216
Loans Excluding Purchased Credit-Impaired Loans [Member] | Commercial real estate mortgage [Member]
By delinquency status:
Loans		130,158	132,108
Over 90 DPD and still accruing		2	36
Nonaccrual loans		630	685
Loans Excluding Purchased Credit-Impaired Loans [Member] | Commercial Real Estate Construction [Member]
By delinquency status:
Loans		25,324	23,859
Over 90 DPD and still accruing		10	0
Nonaccrual loans		34	43
Loans Excluding Purchased Credit-Impaired Loans [Member] | Commercial Lease Financing Receivable [Member]
By delinquency status:
Loans		19,174	19,289
Over 90 DPD and still accruing		0	0
Nonaccrual loans		89	115
PCI Loans Carrying Value [Member]
By delinquency status:
PCI loans		14,273	16,731
PCI Loans Carrying Value [Member] | Total Commercial [Member]
By delinquency status:
PCI loans		263	677	$ 18,700
PCI Loans Carrying Value [Member] | Commercial and Industrial Loans [Member]
By delinquency status:
PCI loans		131	237
PCI Loans Carrying Value [Member] | Commercial real estate mortgage [Member]
By delinquency status:
PCI loans		119	383
PCI Loans Carrying Value [Member] | Commercial Real Estate Construction [Member]
By delinquency status:
PCI loans		13	57
PCI Loans Carrying Value [Member] | Commercial Lease Financing Receivable [Member]
By delinquency status:
PCI loans		0	0
Pass [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Total Commercial [Member]
By delinquency status:
Loans		480,229	476,266
Pass [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Commercial and Industrial Loans [Member]
By delinquency status:
Loans		311,963	308,166
Pass [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Commercial real estate mortgage [Member]
By delinquency status:
Loans		125,283	126,793
Pass [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Commercial Real Estate Construction [Member]
By delinquency status:
Loans		25,013	23,408
Pass [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Commercial Lease Financing Receivable [Member]
By delinquency status:
Loans		17,970	17,899
Criticized [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Total Commercial [Member]
By delinquency status:
Loans		25,409	29,593
Criticized [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Commercial and Industrial Loans [Member]
By delinquency status:
Loans		19,019	22,437
Criticized [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Commercial real estate mortgage [Member]
By delinquency status:
Loans		4,875	5,315
Criticized [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Commercial Real Estate Construction [Member]
By delinquency status:
Loans		311	451
Criticized [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Commercial Lease Financing Receivable [Member]
By delinquency status:
Loans		1,204	1,390
Current-29 days past due (DPD) and still accruing [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Total Commercial [Member]
By delinquency status:
Loans		501,092	500,748
Current-29 days past due (DPD) and still accruing [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Commercial and Industrial Loans [Member]
By delinquency status:
Loans		327,614	326,765
Current-29 days past due (DPD) and still accruing [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Commercial real estate mortgage [Member]
By delinquency status:
Loans		129,360	131,165
Current-29 days past due (DPD) and still accruing [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Commercial Real Estate Construction [Member]
By delinquency status:
Loans		25,148	23,776
Current-29 days past due (DPD) and still accruing [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Commercial Lease Financing Receivable [Member]
By delinquency status:
Loans		18,970	19,042
30-89 days past due and still accruing [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Total Commercial [Member]
By delinquency status:
Loans		1,107	988
30-89 days past due and still accruing [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Commercial and Industrial Loans [Member]
By delinquency status:
Loans		694	594
30-89 days past due and still accruing [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Commercial real estate mortgage [Member]
By delinquency status:
Loans		166	222
30-89 days past due and still accruing [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Commercial Real Estate Construction [Member]
By delinquency status:
Loans		132	40
30-89 days past due and still accruing [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Commercial Lease Financing Receivable [Member]
By delinquency status:
Loans		$ 115	$ 132

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