Loans and Allowance for Loan Losses - Summary of Nonaccrual Loans (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Nonaccrual loans
Nonaccrual loans	$ 634	$ 421
Troubled debt restructured loans that continue to accrue interest	296	299
Troubled debt restructured nonaccrual loans (included in the total nonaccrual loans above)	163	136
Commercial
Nonaccrual loans
Nonaccrual loans	490	281
Consumer
Nonaccrual loans
Nonaccrual loans	144	140
Residential mortgage | Consumer Loans
Nonaccrual loans
Nonaccrual loans	124	121
Home equity and other consumer loans | Consumer Loans
Nonaccrual loans
Nonaccrual loans	20	19
Commercial mortgage | Commercial Loans
Nonaccrual loans
Nonaccrual loans	12	12
Commercial and industrial | Commercial Loans
Nonaccrual loans
Nonaccrual loans	$ 478	$ 269