Loans - Consumer, Excluding Credit Card Loan Portfolio (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Loans and Leases Receivable Disclosure [Line Items]
Retained	$ 969,415	$ 924,838	$ 889,907
Consumer, excluding credit card
Loans and Leases Receivable Disclosure [Line Items]
Retained	373,637	372,553	$ 364,406
Consumer, excluding credit card | Residential mortgage
Loans and Leases Receivable Disclosure [Line Items]
Retained	231,078	216,496
Consumer, excluding credit card | Residential mortgage | Residential real estate – PCI
Loans and Leases Receivable Disclosure [Line Items]
Retained	24,034	30,576
Consumer, excluding credit card | Home equity
Loans and Leases Receivable Disclosure [Line Items]
Retained	28,340	33,450
Consumer, excluding credit card | Home equity | Residential real estate – PCI
Loans and Leases Receivable Disclosure [Line Items]
Retained	8,963	10,799
Consumer, excluding credit card | Auto
Loans and Leases Receivable Disclosure [Line Items]
Retained	63,573	66,242
Consumer, excluding credit card | Consumer & Business Banking
Loans and Leases Receivable Disclosure [Line Items]
Retained	26,612	25,789
Consumer, excluding credit card | Mortgages | Prime mortgage | Residential real estate – PCI
Loans and Leases Receivable Disclosure [Line Items]
Retained	4,690	6,479
Consumer, excluding credit card | Mortgages | Subprime mortgage | Residential real estate – PCI
Loans and Leases Receivable Disclosure [Line Items]
Retained	1,945	2,609
Consumer, excluding credit card | Option ARMs | Residential real estate – PCI
Loans and Leases Receivable Disclosure [Line Items]
Retained	$ 8,436	$ 10,689