Loans - Consumer, Excluding Credit Card Loan Portfolio, Other Consumer Loans (Details) - USD ($)	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 947,728,000,000	$ 969,415,000,000	$ 940,440,000,000
Consumer, excluding credit card
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	351,692,000,000	373,637,000,000	$ 374,587,000,000
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	$ 62,073,000,000	$ 63,573,000,000
% of 30 plus days past due to total retained loans	0.82%	0.93%
Nonaccrual loans	$ 108,000,000	$ 128,000,000
Consumer, excluding credit card | Auto | Noncriticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	14,754,000,000	15,749,000,000
Consumer, excluding credit card | Auto | Criticized performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	407,000,000	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	8,142,000,000	8,330,000,000
Consumer, excluding credit card | Auto | Texas
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	6,524,000,000	6,531,000,000
Consumer, excluding credit card | Auto | New York
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	3,690,000,000	3,863,000,000
Consumer, excluding credit card | Auto | Illinois
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	3,625,000,000	3,716,000,000
Consumer, excluding credit card | Auto | Florida
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	3,256,000,000	3,256,000,000
Consumer, excluding credit card | Auto | Arizona
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	2,011,000,000	2,084,000,000
Consumer, excluding credit card | Auto | Ohio
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,927,000,000	1,973,000,000
Consumer, excluding credit card | Auto | New Jersey
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,936,000,000	1,981,000,000
Consumer, excluding credit card | Auto | Michigan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,305,000,000	1,357,000,000
Consumer, excluding credit card | Auto | Louisiana
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,539,000,000	1,587,000,000
Consumer, excluding credit card | Auto | All other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	28,118,000,000	28,895,000,000
Consumer, excluding credit card | Auto | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	61,562,000,000	62,984,000,000
Consumer, excluding credit card | Auto | 30–119 days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	511,000,000	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	$ 26,616,000,000	$ 26,612,000,000
% of 30 plus days past due to total retained loans	1.23%	1.36%
Nonaccrual loans	$ 223,000,000	$ 245,000,000
Consumer, excluding credit card | Consumer & Business Banking | Noncriticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	18,707,000,000	18,743,000,000
Consumer, excluding credit card | Consumer & Business Banking | Criticized performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	730,000,000	751,000,000
Consumer, excluding credit card | Consumer & Business Banking | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	171,000,000	191,000,000
Consumer, excluding credit card | Consumer & Business Banking | California
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	5,689,000,000	5,520,000,000
Consumer, excluding credit card | Consumer & Business Banking | Texas
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	3,060,000,000	2,993,000,000
Consumer, excluding credit card | Consumer & Business Banking | New York
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	4,349,000,000	4,381,000,000
Consumer, excluding credit card | Consumer & Business Banking | Illinois
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,731,000,000	2,046,000,000
Consumer, excluding credit card | Consumer & Business Banking | Florida
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,519,000,000	1,502,000,000
Consumer, excluding credit card | Consumer & Business Banking | Arizona
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,275,000,000	1,491,000,000
Consumer, excluding credit card | Consumer & Business Banking | Ohio
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,210,000,000	1,305,000,000
Consumer, excluding credit card | Consumer & Business Banking | New Jersey
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	811,000,000	723,000,000
Consumer, excluding credit card | Consumer & Business Banking | Michigan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,264,000,000	1,329,000,000
Consumer, excluding credit card | Consumer & Business Banking | Louisiana
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	789,000,000	860,000,000
Consumer, excluding credit card | Consumer & Business Banking | All other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	4,919,000,000	4,462,000,000
Consumer, excluding credit card | Consumer & Business Banking | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	26,289,000,000	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	215,000,000	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	112,000,000	111,000,000
Consumer, excluding credit card | Total other consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 88,689,000,000	$ 90,185,000,000
% of 30 plus days past due to total retained loans	0.94%	1.06%
Nonaccrual loans	$ 331,000,000	$ 373,000,000
Consumer, excluding credit card | Total other consumer | Noncriticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	33,461,000,000	34,492,000,000
Consumer, excluding credit card | Total other consumer | Criticized performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,137,000,000	1,024,000,000
Consumer, excluding credit card | Total other consumer | Criticized nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	171,000,000	191,000,000
Consumer, excluding credit card | Total other consumer | California
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	13,831,000,000	13,850,000,000
Consumer, excluding credit card | Total other consumer | Texas
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	9,584,000,000	9,524,000,000
Consumer, excluding credit card | Total other consumer | New York
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	8,039,000,000	8,244,000,000
Consumer, excluding credit card | Total other consumer | Illinois
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	5,356,000,000	5,762,000,000
Consumer, excluding credit card | Total other consumer | Florida
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	4,775,000,000	4,758,000,000
Consumer, excluding credit card | Total other consumer | Arizona
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	3,286,000,000	3,575,000,000
Consumer, excluding credit card | Total other consumer | Ohio
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	3,137,000,000	3,278,000,000
Consumer, excluding credit card | Total other consumer | New Jersey
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	2,747,000,000	2,704,000,000
Consumer, excluding credit card | Total other consumer | Michigan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	2,569,000,000	2,686,000,000
Consumer, excluding credit card | Total other consumer | Louisiana
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	2,328,000,000	2,447,000,000
Consumer, excluding credit card | Total other consumer | All other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	33,037,000,000	33,357,000,000
Consumer, excluding credit card | Total other consumer | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	87,851,000,000	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	726,000,000	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	$ 112,000,000	$ 111,000,000