Loans - Consumer, Excluding Credit Card Loans, Other Consumer Loans (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Loans and Leases Receivable Disclosure [Line Items]
Retained	$ 969,415,000,000	$ 924,838,000,000	$ 889,907,000,000
Consumer, excluding credit card
Loans and Leases Receivable Disclosure [Line Items]
Retained	373,637,000,000	372,553,000,000	$ 364,406,000,000
90 or more days past due and still accruing	0	0
Consumer, excluding credit card | Total other consumer
Loans and Leases Receivable Disclosure [Line Items]
Retained	$ 90,185,000,000	$ 92,031,000,000
% of 30 plus days past due to total retained loans	1.06%	1.01%
Nonaccrual loans	$ 373,000,000	$ 424,000,000
Consumer, excluding credit card | Total other consumer | Noncriticized
Loans and Leases Receivable Disclosure [Line Items]
Retained	34,492,000,000	33,542,000,000
Consumer, excluding credit card | Total other consumer | Criticized performing
Loans and Leases Receivable Disclosure [Line Items]
Retained	1,024,000,000	884,000,000
Consumer, excluding credit card | Total other consumer | Criticized nonaccrual
Loans and Leases Receivable Disclosure [Line Items]
Retained	191,000,000	222,000,000
Consumer, excluding credit card | Total other consumer | California
Loans and Leases Receivable Disclosure [Line Items]
Retained	13,850,000,000	13,477,000,000
Consumer, excluding credit card | Total other consumer | Texas
Loans and Leases Receivable Disclosure [Line Items]
Retained	9,524,000,000	9,929,000,000
Consumer, excluding credit card | Total other consumer | New York
Loans and Leases Receivable Disclosure [Line Items]
Retained	8,244,000,000	8,218,000,000
Consumer, excluding credit card | Total other consumer | Illinois
Loans and Leases Receivable Disclosure [Line Items]
Retained	5,762,000,000	5,933,000,000
Consumer, excluding credit card | Total other consumer | Florida
Loans and Leases Receivable Disclosure [Line Items]
Retained	4,758,000,000	4,774,000,000
Consumer, excluding credit card | Total other consumer | Arizona
Loans and Leases Receivable Disclosure [Line Items]
Retained	3,575,000,000	3,604,000,000
Consumer, excluding credit card | Total other consumer | Ohio
Loans and Leases Receivable Disclosure [Line Items]
Retained	3,278,000,000	3,485,000,000
Consumer, excluding credit card | Total other consumer | New Jersey
Loans and Leases Receivable Disclosure [Line Items]
Retained	2,704,000,000	2,765,000,000
Consumer, excluding credit card | Total other consumer | Michigan
Loans and Leases Receivable Disclosure [Line Items]
Retained	2,686,000,000	2,775,000,000
Consumer, excluding credit card | Total other consumer | Louisiana
Loans and Leases Receivable Disclosure [Line Items]
Retained	2,447,000,000	2,505,000,000
Consumer, excluding credit card | Total other consumer | All other
Loans and Leases Receivable Disclosure [Line Items]
Retained	33,357,000,000	34,566,000,000
Consumer, excluding credit card | Auto
Loans and Leases Receivable Disclosure [Line Items]
Retained	$ 63,573,000,000	$ 66,242,000,000
% of 30 plus days past due to total retained loans	0.93%	0.89%
Nonaccrual loans	$ 128,000,000	$ 141,000,000
Consumer, excluding credit card | Auto | Noncriticized
Loans and Leases Receivable Disclosure [Line Items]
Retained	15,749,000,000	15,604,000,000
Consumer, excluding credit card | Auto | Criticized performing
Loans and Leases Receivable Disclosure [Line Items]
Retained	273,000,000	93,000,000
Consumer, excluding credit card | Auto | Criticized nonaccrual
Loans and Leases Receivable Disclosure [Line Items]
Retained	0	9,000,000
Consumer, excluding credit card | Auto | California
Loans and Leases Receivable Disclosure [Line Items]
Retained	8,330,000,000	8,445,000,000
Consumer, excluding credit card | Auto | Texas
Loans and Leases Receivable Disclosure [Line Items]
Retained	6,531,000,000	7,013,000,000
Consumer, excluding credit card | Auto | New York
Loans and Leases Receivable Disclosure [Line Items]
Retained	3,863,000,000	4,023,000,000
Consumer, excluding credit card | Auto | Illinois
Loans and Leases Receivable Disclosure [Line Items]
Retained	3,716,000,000	3,916,000,000
Consumer, excluding credit card | Auto | Florida
Loans and Leases Receivable Disclosure [Line Items]
Retained	3,256,000,000	3,350,000,000
Consumer, excluding credit card | Auto | Arizona
Loans and Leases Receivable Disclosure [Line Items]
Retained	2,084,000,000	2,221,000,000
Consumer, excluding credit card | Auto | Ohio
Loans and Leases Receivable Disclosure [Line Items]
Retained	1,973,000,000	2,105,000,000
Consumer, excluding credit card | Auto | New Jersey
Loans and Leases Receivable Disclosure [Line Items]
Retained	1,981,000,000	2,044,000,000
Consumer, excluding credit card | Auto | Michigan
Loans and Leases Receivable Disclosure [Line Items]
Retained	1,357,000,000	1,418,000,000
Consumer, excluding credit card | Auto | Louisiana
Loans and Leases Receivable Disclosure [Line Items]
Retained	1,587,000,000	1,656,000,000
Consumer, excluding credit card | Auto | All other
Loans and Leases Receivable Disclosure [Line Items]
Retained	28,895,000,000	30,051,000,000
Consumer, excluding credit card | Consumer & Business Banking
Loans and Leases Receivable Disclosure [Line Items]
Retained	$ 26,612,000,000	$ 25,789,000,000
% of 30 plus days past due to total retained loans	1.36%	1.30%
Nonaccrual loans	$ 245,000,000	$ 283,000,000
Consumer, excluding credit card | Consumer & Business Banking | Noncriticized
Loans and Leases Receivable Disclosure [Line Items]
Retained	18,743,000,000	17,938,000,000
Consumer, excluding credit card | Consumer & Business Banking | Criticized performing
Loans and Leases Receivable Disclosure [Line Items]
Retained	751,000,000	791,000,000
Consumer, excluding credit card | Consumer & Business Banking | Criticized nonaccrual
Loans and Leases Receivable Disclosure [Line Items]
Retained	191,000,000	213,000,000
Consumer, excluding credit card | Consumer & Business Banking | California
Loans and Leases Receivable Disclosure [Line Items]
Retained	5,520,000,000	5,032,000,000
Consumer, excluding credit card | Consumer & Business Banking | Texas
Loans and Leases Receivable Disclosure [Line Items]
Retained	2,993,000,000	2,916,000,000
Consumer, excluding credit card | Consumer & Business Banking | New York
Loans and Leases Receivable Disclosure [Line Items]
Retained	4,381,000,000	4,195,000,000
Consumer, excluding credit card | Consumer & Business Banking | Illinois
Loans and Leases Receivable Disclosure [Line Items]
Retained	2,046,000,000	2,017,000,000
Consumer, excluding credit card | Consumer & Business Banking | Florida
Loans and Leases Receivable Disclosure [Line Items]
Retained	1,502,000,000	1,424,000,000
Consumer, excluding credit card | Consumer & Business Banking | Arizona
Loans and Leases Receivable Disclosure [Line Items]
Retained	1,491,000,000	1,383,000,000
Consumer, excluding credit card | Consumer & Business Banking | Ohio
Loans and Leases Receivable Disclosure [Line Items]
Retained	1,305,000,000	1,380,000,000
Consumer, excluding credit card | Consumer & Business Banking | New Jersey
Loans and Leases Receivable Disclosure [Line Items]
Retained	723,000,000	721,000,000
Consumer, excluding credit card | Consumer & Business Banking | Michigan
Loans and Leases Receivable Disclosure [Line Items]
Retained	1,329,000,000	1,357,000,000
Consumer, excluding credit card | Consumer & Business Banking | Louisiana
Loans and Leases Receivable Disclosure [Line Items]
Retained	860,000,000	849,000,000
Consumer, excluding credit card | Consumer & Business Banking | All other
Loans and Leases Receivable Disclosure [Line Items]
Retained	4,462,000,000	4,515,000,000
Consumer, excluding credit card | Current | Total other consumer
Loans and Leases Receivable Disclosure [Line Items]
Retained	89,233,000,000	91,105,000,000
Consumer, excluding credit card | Current | Auto
Loans and Leases Receivable Disclosure [Line Items]
Retained	62,984,000,000	65,651,000,000
Consumer, excluding credit card | Current | Consumer & Business Banking
Loans and Leases Receivable Disclosure [Line Items]
Retained	26,249,000,000	25,454,000,000
Consumer, excluding credit card | 30–119 days past due | Total other consumer
Loans and Leases Receivable Disclosure [Line Items]
Retained	841,000,000	797,000,000
Consumer, excluding credit card | 30–119 days past due | Auto
Loans and Leases Receivable Disclosure [Line Items]
Retained	589,000,000	584,000,000
Consumer, excluding credit card | 30–119 days past due | Consumer & Business Banking
Loans and Leases Receivable Disclosure [Line Items]
Retained	252,000,000	213,000,000
Consumer, excluding credit card | 120 or more days past due | Total other consumer
Loans and Leases Receivable Disclosure [Line Items]
Retained	111,000,000	129,000,000
Consumer, excluding credit card | 120 or more days past due | Auto
Loans and Leases Receivable Disclosure [Line Items]
Retained	0	7,000,000
Consumer, excluding credit card | 120 or more days past due | Consumer & Business Banking
Loans and Leases Receivable Disclosure [Line Items]
Retained	$ 111,000,000	$ 122,000,000