Loans - Consumer, Excluding Credit Card Loan Portfolio (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 943,841	$ 969,415	$ 925,611
Consumer, excluding credit card
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	359,715	373,637	$ 373,243
Consumer, excluding credit card | Residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	220,158	231,078
Consumer, excluding credit card | Residential mortgage | Residential real estate – PCI
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	23,207	24,034
Consumer, excluding credit card | Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	27,072	28,340
Consumer, excluding credit card | Home equity | Residential real estate – PCI
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	8,584	8,963
Consumer, excluding credit card | Auto
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	62,786	63,573
Consumer, excluding credit card | Consumer & Business Banking
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	26,492	26,612
Consumer, excluding credit card | Fixed Rate Residential Mortgage | Prime mortgage | Residential real estate – PCI
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	4,529	4,690
Consumer, excluding credit card | Fixed Rate Residential Mortgage | Subprime mortgage | Residential real estate – PCI
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,909	1,945
Consumer, excluding credit card | Option ARMs | Residential real estate – PCI
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 8,185	$ 8,436