Loans - Consumer, Excluding Credit Card Loan Portfolio, Residential Real Estate, Excluding PCI Loans (Details) - USD ($)	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 947,651,000,000	$ 924,838,000,000	$ 909,182,000,000
Consumer, excluding credit card
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	375,958,000,000	372,553,000,000	$ 369,413,000,000
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	$ 260,679,000,000	$ 249,946,000,000
% of 30 plus days past due to total retained loans	0.75%	1.09%
Nonaccrual loans	$ 3,262,000,000	$ 3,785,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | California
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	80,176,000,000	75,437,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | New York
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	35,162,000,000	34,339,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | Illinois
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	17,450,000,000	17,022,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | Texas
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	15,769,000,000	14,529,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | Florida
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	12,243,000,000	11,445,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | New Jersey
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	9,150,000,000	9,099,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | Washington
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	8,961,000,000	7,988,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | Colorado
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	8,656,000,000	7,967,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | Massachusetts
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	6,791,000,000	6,618,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | Arizona
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	5,730,000,000	5,548,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | All other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	60,591,000,000	59,954,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | U.S. government-guaranteed
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	7,096,000,000	8,495,000,000
90 or more days past due and government guaranteed	2,828,000,000	4,172,000,000
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	7,100,000,000	8,500,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | No FICO/LTV available
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	2,245,000,000	2,948,000,000
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	34,000,000	47,000,000
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	31,000,000	22,000,000
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	158,000,000	332,000,000
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	106,000,000	183,000,000
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	4,665,000,000	6,045,000,000
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	673,000,000	1,052,000,000
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	235,436,000,000	220,020,000,000
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	10,235,000,000	10,802,000,000
Consumer, excluding credit card | Total residential real estate – excluding PCI | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	254,353,000,000	241,104,000,000
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	2,700,000,000	2,400,000,000
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	3,295,000,000	4,905,000,000
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	2,200,000,000	3,200,000,000
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	3,031,000,000	3,937,000,000
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	2,200,000,000	2,900,000,000
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	4,400,000,000	6,100,000,000
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	1,300,000,000	1,500,000,000
Consumer, excluding credit card | Residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 231,361,000,000	$ 216,496,000,000
% of 30 plus days past due to total retained loans	0.51%	0.77%
Nonaccrual loans	$ 1,880,000,000	$ 2,175,000,000
Consumer, excluding credit card | Residential mortgage | California
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	74,324,000,000	68,855,000,000
Consumer, excluding credit card | Residential mortgage | New York
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	29,146,000,000	27,473,000,000
Consumer, excluding credit card | Residential mortgage | Illinois
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	15,242,000,000	14,501,000,000
Consumer, excluding credit card | Residential mortgage | Texas
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	13,926,000,000	12,508,000,000
Consumer, excluding credit card | Residential mortgage | Florida
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	10,624,000,000	9,598,000,000
Consumer, excluding credit card | Residential mortgage | New Jersey
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	7,448,000,000	7,142,000,000
Consumer, excluding credit card | Residential mortgage | Washington
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	8,057,000,000	6,962,000,000
Consumer, excluding credit card | Residential mortgage | Colorado
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	8,131,000,000	7,335,000,000
Consumer, excluding credit card | Residential mortgage | Massachusetts
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	6,545,000,000	6,323,000,000
Consumer, excluding credit card | Residential mortgage | Arizona
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	4,519,000,000	4,109,000,000
Consumer, excluding credit card | Residential mortgage | All other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	53,399,000,000	51,690,000,000
Consumer, excluding credit card | Residential mortgage | U.S. government-guaranteed
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	7,096,000,000	8,495,000,000
90 or more days past due and government guaranteed	2,828,000,000	4,172,000,000
Consumer, excluding credit card | Residential mortgage | No FICO/LTV available
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	888,000,000	1,259,000,000
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	28,000,000	37,000,000
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	30,000,000	19,000,000
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	20,000,000	36,000,000
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	60,000,000	88,000,000
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	3,606,000,000	4,369,000,000
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	314,000,000	483,000,000
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	212,585,000,000	194,758,000,000
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	6,734,000,000	6,952,000,000
Consumer, excluding credit card | Residential mortgage | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	225,799,000,000	208,713,000,000
Consumer, excluding credit card | Residential mortgage | 30–149 days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	2,825,000,000	4,234,000,000
Consumer, excluding credit card | Residential mortgage | 150 or more days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	2,737,000,000	3,549,000,000
Consumer, excluding credit card | Residential mortgage | 90 or more days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	0	0
Consumer, excluding credit card | Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 29,318,000,000	$ 33,450,000,000
% of 30 plus days past due to total retained loans	2.61%	3.17%
Nonaccrual loans	$ 1,382,000,000	$ 1,610,000,000
Consumer, excluding credit card | Home equity | California
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	5,852,000,000	6,582,000,000
Consumer, excluding credit card | Home equity | New York
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	6,016,000,000	6,866,000,000
Consumer, excluding credit card | Home equity | Illinois
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	2,208,000,000	2,521,000,000
Consumer, excluding credit card | Home equity | Texas
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,843,000,000	2,021,000,000
Consumer, excluding credit card | Home equity | Florida
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,619,000,000	1,847,000,000
Consumer, excluding credit card | Home equity | New Jersey
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,702,000,000	1,957,000,000
Consumer, excluding credit card | Home equity | Washington
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	904,000,000	1,026,000,000
Consumer, excluding credit card | Home equity | Colorado
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	525,000,000	632,000,000
Consumer, excluding credit card | Home equity | Massachusetts
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	246,000,000	295,000,000
Consumer, excluding credit card | Home equity | Arizona
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,211,000,000	1,439,000,000
Consumer, excluding credit card | Home equity | All other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	7,192,000,000	8,264,000,000
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	1,357,000,000	1,689,000,000
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	6,000,000	10,000,000
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	3,000,000
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	138,000,000	296,000,000
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	46,000,000	95,000,000
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	1,059,000,000	1,676,000,000
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	359,000,000	569,000,000
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	22,851,000,000	25,262,000,000
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	3,501,000,000	3,850,000,000
Consumer, excluding credit card | Home equity | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	28,554,000,000	32,391,000,000
Consumer, excluding credit card | Home equity | 30–149 days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	470,000,000	671,000,000
Consumer, excluding credit card | Home equity | 150 or more days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 294,000,000	$ 388,000,000