Outstanding Loans and Leases - Consumer Real Estate - Modification Programs (Details) - Consumer real estate - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Financing Receivable, Modifications [Line Items]
Total modifications	$ 152	$ 285	$ 395	$ 991
Modifications under government programs
Financing Receivable, Modifications [Line Items]
Total modifications	8	12	32	48
Modifications under proprietary programs
Financing Receivable, Modifications [Line Items]
Total modifications	18	33	125	446
Loans discharged in Chapter 7 bankruptcy
Financing Receivable, Modifications [Line Items]
Total modifications	16	39	54	121
Trial modifications
Financing Receivable, Modifications [Line Items]
Total modifications	$ 110	$ 201	$ 184	376
Hurricane-Related Modifications \| Modifications under government programs
Financing Receivable, Modifications [Line Items]
Total modifications				$ 197