Loans - Consumer, Excluding Credit Card Loan Portfolio, Other Consumer 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 still accruing	0	0
Consumer, excluding credit card | Auto
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 62,786,000,000	$ 63,573,000,000
% of 30 plus days past due to total retained loans	0.63%	0.93%
Nonaccrual loans	$ 111,000,000	$ 128,000,000
Consumer, excluding credit card | Auto | Noncriticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	15,506,000,000	15,749,000,000
Consumer, excluding credit card | Auto | Criticized performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	246,000,000	273,000,000
Consumer, excluding credit card | Auto | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	0	0
Consumer, excluding credit card | Auto | California
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	8,201,000,000	8,330,000,000
Consumer, excluding credit card | Auto | Texas
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	6,489,000,000	6,531,000,000
Consumer, excluding credit card | Auto | New York
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	3,800,000,000	3,863,000,000
Consumer, excluding credit card | Auto | Illinois
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	3,631,000,000	3,716,000,000
Consumer, excluding credit card | Auto | Florida
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	3,243,000,000	3,256,000,000
Consumer, excluding credit card | Auto | Arizona
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	2,042,000,000	2,084,000,000
Consumer, excluding credit card | Auto | Ohio
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,964,000,000	1,973,000,000
Consumer, excluding credit card | Auto | New Jersey
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,972,000,000	1,981,000,000
Consumer, excluding credit card | Auto | Michigan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,331,000,000	1,357,000,000
Consumer, excluding credit card | Auto | Colorado
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,679,000,000	1,722,000,000
Consumer, excluding credit card | Auto | All other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	28,434,000,000	28,760,000,000
Consumer, excluding credit card | Auto | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	62,389,000,000	62,984,000,000
Consumer, excluding credit card | Auto | 30–119 days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	397,000,000	589,000,000
Consumer, excluding credit card | Auto | 120 or more days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	0	0
Consumer, excluding credit card | Consumer & Business Banking
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 26,492,000,000	$ 26,612,000,000
% of 30 plus days past due to total retained loans	1.32%	1.36%
Nonaccrual loans	$ 247,000,000	$ 245,000,000
Consumer, excluding credit card | Consumer & Business Banking | Noncriticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	18,618,000,000	18,743,000,000
Consumer, excluding credit card | Consumer & Business Banking | Criticized performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	742,000,000	751,000,000
Consumer, excluding credit card | Consumer & Business Banking | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	203,000,000	191,000,000
Consumer, excluding credit card | Consumer & Business Banking | California
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	5,676,000,000	5,520,000,000
Consumer, excluding credit card | Consumer & Business Banking | Texas
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	3,010,000,000	2,993,000,000
Consumer, excluding credit card | Consumer & Business Banking | New York
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	4,305,000,000	4,381,000,000
Consumer, excluding credit card | Consumer & Business Banking | Illinois
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,729,000,000	2,046,000,000
Consumer, excluding credit card | Consumer & Business Banking | Florida
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,528,000,000	1,502,000,000
Consumer, excluding credit card | Consumer & Business Banking | Arizona
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,280,000,000	1,491,000,000
Consumer, excluding credit card | Consumer & Business Banking | Ohio
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,222,000,000	1,305,000,000
Consumer, excluding credit card | Consumer & Business Banking | New Jersey
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	791,000,000	723,000,000
Consumer, excluding credit card | Consumer & Business Banking | Michigan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,303,000,000	1,329,000,000
Consumer, excluding credit card | Consumer & Business Banking | Colorado
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	697,000,000	680,000,000
Consumer, excluding credit card | Consumer & Business Banking | All other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	4,951,000,000	4,642,000,000
Consumer, excluding credit card | Consumer & Business Banking | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	26,143,000,000	26,249,000,000
Consumer, excluding credit card | Consumer & Business Banking | 30–119 days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	223,000,000	252,000,000
Consumer, excluding credit card | Consumer & Business Banking | 120 or more days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	126,000,000	111,000,000
Consumer, excluding credit card | Total other consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 89,278,000,000	$ 90,185,000,000
% of 30 plus days past due to total retained loans	0.84%	1.06%
Nonaccrual loans	$ 358,000,000	$ 373,000,000
Consumer, excluding credit card | Total other consumer | Noncriticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	34,124,000,000	34,492,000,000
Consumer, excluding credit card | Total other consumer | Criticized performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	988,000,000	1,024,000,000
Consumer, excluding credit card | Total other consumer | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	203,000,000	191,000,000
Consumer, excluding credit card | Total other consumer | California
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	13,877,000,000	13,850,000,000
Consumer, excluding credit card | Total other consumer | Texas
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	9,499,000,000	9,524,000,000
Consumer, excluding credit card | Total other consumer | New York
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	8,105,000,000	8,244,000,000
Consumer, excluding credit card | Total other consumer | Illinois
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	5,360,000,000	5,762,000,000
Consumer, excluding credit card | Total other consumer | Florida
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	4,771,000,000	4,758,000,000
Consumer, excluding credit card | Total other consumer | Arizona
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	3,322,000,000	3,575,000,000
Consumer, excluding credit card | Total other consumer | Ohio
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	3,186,000,000	3,278,000,000
Consumer, excluding credit card | Total other consumer | New Jersey
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	2,763,000,000	2,704,000,000
Consumer, excluding credit card | Total other consumer | Michigan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	2,634,000,000	2,686,000,000
Consumer, excluding credit card | Total other consumer | Colorado
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	2,376,000,000	2,402,000,000
Consumer, excluding credit card | Total other consumer | All other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	33,385,000,000	33,402,000,000
Consumer, excluding credit card | Total other consumer | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	88,532,000,000	89,233,000,000
Consumer, excluding credit card | Total other consumer | 30–119 days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	620,000,000	841,000,000
Consumer, excluding credit card | Total other consumer | 120 or more days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 126,000,000	$ 111,000,000