Loans - Consumer, Excluding Credit Card Loan Portfolio, Residential Real Estate, Excluding PCI Loans (Details) - USD ($)	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 943,841,000,000	$ 969,415,000,000	$ 925,611,000,000
Consumer, excluding credit card
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	359,715,000,000	373,637,000,000	$ 373,243,000,000
90 or more days past due and government guaranteed	0	0
Consumer, excluding credit card | Total residential real estate – excluding PCI
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 247,230,000,000	$ 259,418,000,000
% of 30 plus days past due to total retained loans	0.73%	0.71%
Nonaccrual loans	$ 3,031,000,000	$ 3,088,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | California
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	77,412,000,000	80,454,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | New York
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	33,044,000,000	34,616,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | Illinois
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	16,633,000,000	17,380,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | Texas
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	14,786,000,000	15,588,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | Florida
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	11,924,000,000	12,279,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | Washington
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	8,809,000,000	9,173,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | Colorado
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	8,376,000,000	8,661,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | New Jersey
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	8,362,000,000	8,944,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | Massachusetts
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	6,575,000,000	6,810,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | Arizona
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	5,264,000,000	5,592,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | All other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	56,045,000,000	59,921,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | U.S. government-guaranteed
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	5,618,000,000	6,917,000,000
90 or more days past due and government guaranteed	2,120,000,000	2,541,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | U.S. government-guaranteed | All other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	5,600,000,000	6,900,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | No FICO/LTV available
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,644,000,000	1,698,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | Greater than 125% and refreshed FICO scores | Equal to or greater than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	29,000,000	31,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | Greater than 125% and refreshed FICO scores | Less than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	12,000,000	14,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | 101% to 125% and refreshed FICO scores | Equal to or greater than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	109,000,000	148,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | 101% to 125% and refreshed FICO scores | Less than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	68,000,000	91,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | 80% to 100% and refreshed FICO scores | Equal to or greater than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	5,332,000,000	4,963,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | 80% to 100% and refreshed FICO scores | Less than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	498,000,000	607,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | Less than 80% and refreshed FICO scores | Equal to or greater than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	224,293,000,000	235,137,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | Less than 80% and refreshed FICO scores | Less than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	9,627,000,000	9,812,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	242,237,000,000	253,510,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | Current | U.S. government-guaranteed
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	2,400,000,000	2,800,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | 30–149 days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	2,578,000,000	3,216,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | 30–149 days past due | U.S. government-guaranteed
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,500,000,000	2,100,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | 150 or more days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	2,415,000,000	2,692,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | 150 or more days past due | U.S. government-guaranteed
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,700,000,000	2,000,000,000.0
Consumer, excluding credit card | Total residential real estate – excluding PCI | 30 or more days past due | U.S. government-guaranteed
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	3,200,000,000	4,100,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | 90 or more days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	0	0
Consumer, excluding credit card | Total residential real estate – excluding PCI | 90 or more days past due | U.S. government-guaranteed
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	880,000,000	999,000,000
Consumer, excluding credit card | Residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 220,158,000,000	$ 231,078,000,000
% of 30 plus days past due to total retained loans	0.53%	0.48%
Nonaccrual loans	$ 1,755,000,000	$ 1,765,000,000
Consumer, excluding credit card | Residential mortgage | California
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	71,894,000,000	74,759,000,000
Consumer, excluding credit card | Residential mortgage | New York
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	27,556,000,000	28,847,000,000
Consumer, excluding credit card | Residential mortgage | Illinois
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	14,607,000,000	15,249,000,000
Consumer, excluding credit card | Residential mortgage | Texas
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	13,034,000,000	13,769,000,000
Consumer, excluding credit card | Residential mortgage | Florida
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	10,428,000,000	10,704,000,000
Consumer, excluding credit card | Residential mortgage | Washington
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	7,974,000,000	8,304,000,000
Consumer, excluding credit card | Residential mortgage | Colorado
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	7,884,000,000	8,140,000,000
Consumer, excluding credit card | Residential mortgage | New Jersey
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	6,804,000,000	7,302,000,000
Consumer, excluding credit card | Residential mortgage | Massachusetts
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	6,350,000,000	6,574,000,000
Consumer, excluding credit card | Residential mortgage | Arizona
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	4,167,000,000	4,434,000,000
Consumer, excluding credit card | Residential mortgage | All other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	49,460,000,000	52,996,000,000
Consumer, excluding credit card | Residential mortgage | U.S. government-guaranteed
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	5,618,000,000	6,917,000,000
90 or more days past due and government guaranteed	2,120,000,000	2,541,000,000
Consumer, excluding credit card | Residential mortgage | No FICO/LTV available
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	826,000,000	813,000,000
Consumer, excluding credit card | Residential mortgage | Greater than 125% and refreshed FICO scores | Equal to or greater than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	24,000,000	25,000,000
Consumer, excluding credit card | Residential mortgage | Greater than 125% and refreshed FICO scores | Less than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	11,000,000	13,000,000
Consumer, excluding credit card | Residential mortgage | 101% to 125% and refreshed FICO scores | Equal to or greater than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	23,000,000	37,000,000
Consumer, excluding credit card | Residential mortgage | 101% to 125% and refreshed FICO scores | Less than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	39,000,000	53,000,000
Consumer, excluding credit card | Residential mortgage | 80% to 100% and refreshed FICO scores | Equal to or greater than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	4,465,000,000	3,977,000,000
Consumer, excluding credit card | Residential mortgage | 80% to 100% and refreshed FICO scores | Less than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	228,000,000	281,000,000
Consumer, excluding credit card | Residential mortgage | Less than 80% and refreshed FICO scores | Equal to or greater than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	202,482,000,000	212,505,000,000
Consumer, excluding credit card | Residential mortgage | Less than 80% and refreshed FICO scores | Less than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	6,442,000,000	6,457,000,000
Consumer, excluding credit card | Residential mortgage | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	215,815,000,000	225,899,000,000
Consumer, excluding credit card | Residential mortgage | 30–149 days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	2,179,000,000	2,763,000,000
Consumer, excluding credit card | Residential mortgage | 150 or more days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	2,164,000,000	2,416,000,000
Consumer, excluding credit card | Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 27,072,000,000	$ 28,340,000,000
% of 30 plus days past due to total retained loans	2.40%	2.57%
Nonaccrual loans	$ 1,276,000,000	$ 1,323,000,000
Consumer, excluding credit card | Home equity | California
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	5,518,000,000	5,695,000,000
Consumer, excluding credit card | Home equity | New York
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	5,488,000,000	5,769,000,000
Consumer, excluding credit card | Home equity | Illinois
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	2,026,000,000	2,131,000,000
Consumer, excluding credit card | Home equity | Texas
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,752,000,000	1,819,000,000
Consumer, excluding credit card | Home equity | Florida
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,496,000,000	1,575,000,000
Consumer, excluding credit card | Home equity | Washington
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	835,000,000	869,000,000
Consumer, excluding credit card | Home equity | Colorado
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	492,000,000	521,000,000
Consumer, excluding credit card | Home equity | New Jersey
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,558,000,000	1,642,000,000
Consumer, excluding credit card | Home equity | Massachusetts
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	225,000,000	236,000,000
Consumer, excluding credit card | Home equity | Arizona
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,097,000,000	1,158,000,000
Consumer, excluding credit card | Home equity | All other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	6,585,000,000	6,925,000,000
Consumer, excluding credit card | Home equity | U.S. government-guaranteed
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	0	0
90 or more days past due and government guaranteed	0	0
Consumer, excluding credit card | Home equity | No FICO/LTV available
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	818,000,000	885,000,000
Consumer, excluding credit card | Home equity | Greater than 125% and refreshed FICO scores | Equal to or greater than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	5,000,000	6,000,000
Consumer, excluding credit card | Home equity | Greater than 125% and refreshed FICO scores | Less than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,000,000	1,000,000
Consumer, excluding credit card | Home equity | 101% to 125% and refreshed FICO scores | Equal to or greater than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	86,000,000	111,000,000
Consumer, excluding credit card | Home equity | 101% to 125% and refreshed FICO scores | Less than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	29,000,000	38,000,000
Consumer, excluding credit card | Home equity | 80% to 100% and refreshed FICO scores | Equal to or greater than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	867,000,000	986,000,000
Consumer, excluding credit card | Home equity | 80% to 100% and refreshed FICO scores | Less than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	270,000,000	326,000,000
Consumer, excluding credit card | Home equity | Less than 80% and refreshed FICO scores | Equal to or greater than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	21,811,000,000	22,632,000,000
Consumer, excluding credit card | Home equity | Less than 80% and refreshed FICO scores | Less than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	3,185,000,000	3,355,000,000
Consumer, excluding credit card | Home equity | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	26,422,000,000	27,611,000,000
Consumer, excluding credit card | Home equity | 30–149 days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	399,000,000	453,000,000
Consumer, excluding credit card | Home equity | 150 or more days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 251,000,000	$ 276,000,000