Loans and Allowance for Loan Losses - Summary of Nonaccrual Loans (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Nonaccrual loans
Nonaccrual loans	$ 323	$ 328
Troubled debt restructured loans that continue to accrue interest	331	392
Troubled debt restructured nonaccrual loans (included in the total nonaccrual loans above)	145	171
Commercial
Nonaccrual loans
Nonaccrual loans	174	190
Consumer
Nonaccrual loans
Nonaccrual loans	149	138
residential mortgage and home equity [Member] | Consumer Loans
Nonaccrual loans
Nonaccrual loans	146	137
Other consumer(2) | Consumer Loans
Nonaccrual loans
Nonaccrual loans	3	1
Commercial mortgage | Commercial Loans
Nonaccrual loans
Nonaccrual loans	16	15
Construction [Member] | Commercial Loans
Nonaccrual loans
Nonaccrual loans	55
Commercial and industrial | Commercial Loans
Nonaccrual loans
Nonaccrual loans	$ 103	175
Construction | Commercial Loans
Nonaccrual loans
Nonaccrual loans		$ 0