Loans and Allowance for Credit Losses, Loans by FICO Score, Consumer (Details) - USD ($) $ in Millions		Jun. 30, 2017	Dec. 31, 2016	Dec. 31, 2008
By FICO:
Loans	[1]	$ 957,423	$ 967,604
Total Consumer [Member]
By FICO:
Loans		451,522	461,068
90 days or more past due and still accruing		789	908
Real estate 1-4 family first mortgage [Member]
By FICO:
Loans		276,566	275,579
Real estate 1-4 family junior lien mortgage [Member]
By FICO:
Loans		42,747	46,237
Credit Card [Member]
By FICO:
Loans		35,305	36,700
Automobile [Member]
By FICO:
Loans		57,958	62,286
Other revolving credit and installment [Member]
By FICO:
Loans		38,946	40,266
Loans Excluding Purchased Credit-Impaired Loans [Member]
By FICO:
90 days or more past due and still accruing		9,716	11,858
Loans Excluding Purchased Credit-Impaired Loans [Member] | Total Consumer [Member]
By FICO:
Loans		437,512	445,014
Loans Excluding Purchased Credit-Impaired Loans [Member] | Real estate 1-4 family first mortgage [Member]
By FICO:
Loans		262,587	259,561
Loans Excluding Purchased Credit-Impaired Loans [Member] | Real estate 1-4 family junior lien mortgage [Member]
By FICO:
Loans		42,716	46,201
Loans Excluding Purchased Credit-Impaired Loans [Member] | Credit Card [Member]
By FICO:
Loans		35,305	36,700
Loans Excluding Purchased Credit-Impaired Loans [Member] | Automobile [Member]
By FICO:
Loans		57,958	62,286
Loans Excluding Purchased Credit-Impaired Loans [Member] | Other revolving credit and installment [Member]
By FICO:
Loans		38,946	40,266
PCI Loans Carrying Value [Member]
By FICO:
PCI loans		14,273	16,731
PCI Loans Carrying Value [Member] | Total Consumer [Member]
By FICO:
PCI loans		14,010	16,054	$ 40,100
PCI Loans Carrying Value [Member] | Real estate 1-4 family first mortgage [Member]
By FICO:
PCI loans		13,979	16,018
PCI Loans Carrying Value [Member] | Real estate 1-4 family junior lien mortgage [Member]
By FICO:
PCI loans		31	36
PCI Loans Carrying Value [Member] | Credit Card [Member]
By FICO:
PCI loans		0	0
PCI Loans Carrying Value [Member] | Automobile [Member]
By FICO:
PCI loans		0	0
PCI Loans Carrying Value [Member] | Other revolving credit and installment [Member]
By FICO:
PCI loans		0	0
FICO less than 600 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Total Consumer [Member]
By FICO:
Loans		21,606	23,696
FICO less than 600 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Real estate 1-4 family first mortgage [Member]
By FICO:
Loans		5,767	6,720
FICO less than 600 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Real estate 1-4 family junior lien mortgage [Member]
By FICO:
Loans		1,949	2,591
FICO less than 600 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Credit Card [Member]
By FICO:
Loans		3,282	3,475
FICO less than 600 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Automobile [Member]
By FICO:
Loans		9,716	9,934
FICO less than 600 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Other revolving credit and installment [Member]
By FICO:
Loans		892	976
FICO 600-639 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Total Consumer [Member]
By FICO:
Loans		15,684	18,187
FICO 600-639 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Real estate 1-4 family first mortgage [Member]
By FICO:
Loans		3,917	5,400
FICO 600-639 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Real estate 1-4 family junior lien mortgage [Member]
By FICO:
Loans		1,422	1,917
FICO 600-639 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Credit Card [Member]
By FICO:
Loans		2,932	3,109
FICO 600-639 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Automobile [Member]
By FICO:
Loans		6,468	6,705
FICO 600-639 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Other revolving credit and installment [Member]
By FICO:
Loans		945	1,056
FICO 640-679 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Total Consumer [Member]
By FICO:
Loans		26,219	32,937
FICO 640-679 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Real estate 1-4 family first mortgage [Member]
By FICO:
Loans		7,322	10,975
FICO 640-679 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Real estate 1-4 family junior lien mortgage [Member]
By FICO:
Loans		2,689	3,747
FICO 640-679 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Credit Card [Member]
By FICO:
Loans		5,399	5,678
FICO 640-679 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Automobile [Member]
By FICO:
Loans		8,741	10,204
FICO 640-679 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Other revolving credit and installment [Member]
By FICO:
Loans		2,068	2,333
FICO 680-719 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Total Consumer [Member]
By FICO:
Loans		41,462	52,649
FICO 680-719 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Real estate 1-4 family first mortgage [Member]
By FICO:
Loans		15,579	23,300
FICO 680-719 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Real estate 1-4 family junior lien mortgage [Member]
By FICO:
Loans		5,269	6,432
FICO 680-719 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Credit Card [Member]
By FICO:
Loans		7,195	7,382
FICO 680-719 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Automobile [Member]
By FICO:
Loans		9,676	11,233
FICO 680-719 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Other revolving credit and installment [Member]
By FICO:
Loans		3,743	4,302
FICO 720-759 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Total Consumer [Member]
By FICO:
Loans		56,369	70,515
FICO 720-759 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Real estate 1-4 family first mortgage [Member]
By FICO:
Loans		28,480	38,832
FICO 720-759 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Real estate 1-4 family junior lien mortgage [Member]
By FICO:
Loans		6,756	9,413
FICO 720-759 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Credit Card [Member]
By FICO:
Loans		7,544	7,632
FICO 720-759 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Automobile [Member]
By FICO:
Loans		8,282	8,769
FICO 720-759 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Other revolving credit and installment [Member]
By FICO:
Loans		5,307	5,869
FICO 760-799 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Total Consumer [Member]
By FICO:
Loans		81,279	141,240
FICO 760-799 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Real estate 1-4 family first mortgage [Member]
By FICO:
Loans		54,249	103,608
FICO 760-799 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Real estate 1-4 family junior lien mortgage [Member]
By FICO:
Loans		7,792	14,929
FICO 760-799 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Credit Card [Member]
By FICO:
Loans		6,018	6,191
FICO 760-799 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Automobile [Member]
By FICO:
Loans		6,739	8,164
FICO 760-799 [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Other revolving credit and installment [Member]
By FICO:
Loans		6,481	8,348
FICO 800 or more [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Total Consumer [Member]
By FICO:
Loans		163,675	72,057
FICO 800 or more [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Real estate 1-4 family first mortgage [Member]
By FICO:
Loans		127,929	49,508
FICO 800 or more [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Real estate 1-4 family junior lien mortgage [Member]
By FICO:
Loans		16,015	6,391
FICO 800 or more [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Credit Card [Member]
By FICO:
Loans		2,889	2,868
FICO 800 or more [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Automobile [Member]
By FICO:
Loans		8,098	6,856
FICO 800 or more [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Other revolving credit and installment [Member]
By FICO:
Loans		8,744	6,434
No FICO available [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Total Consumer [Member]
By FICO:
Loans		9,471	10,086
No FICO available [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Real estate 1-4 family first mortgage [Member]
By FICO:
Loans		5,755	5,613
No FICO available [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Real estate 1-4 family junior lien mortgage [Member]
By FICO:
Loans		824	781
No FICO available [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Credit Card [Member]
By FICO:
Loans		46	365
No FICO available [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Automobile [Member]
By FICO:
Loans		238	421
No FICO available [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Other revolving credit and installment [Member]
By FICO:
Loans		2,608	2,906
FICO not required [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Total Consumer [Member]
By FICO:
Loans		8,158	8,042
FICO not required [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Real estate 1-4 family first mortgage [Member]
By FICO:
Loans		0	0
FICO not required [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Real estate 1-4 family junior lien mortgage [Member]
By FICO:
Loans		0	0
FICO not required [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Credit Card [Member]
By FICO:
Loans		0	0
FICO not required [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Automobile [Member]
By FICO:
Loans		0	0
FICO not required [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Other revolving credit and installment [Member]
By FICO:
Loans		8,158	8,042
Government Insured or Guaranteed [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Total Consumer [Member]
By FICO:
Loans		13,589	15,605
Government Insured or Guaranteed [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Real estate 1-4 family first mortgage [Member]
By FICO:
Loans		13,589	15,605
Government Insured or Guaranteed [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Real estate 1-4 family junior lien mortgage [Member]
By FICO:
Loans		0	0
Government Insured or Guaranteed [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Credit Card [Member]
By FICO:
Loans		0	0
Government Insured or Guaranteed [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Automobile [Member]
By FICO:
Loans		0	0
Government Insured or Guaranteed [Member] | Loans Excluding Purchased Credit-Impaired Loans [Member] | Other revolving credit and installment [Member]
By FICO:
Loans		$ 0	$ 0

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