Loan Portfolio - Loans by Category (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 106,159	$ 94,646
Accrued interest	225	244
Commercial Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	78,205	68,032
Accrued interest	121
Consumer Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	27,954	26,614
Accrued interest	104
Commercial and industrial | Commercial Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	58,297	48,295
Commercial mortgage | Commercial Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	13,465	13,491
Real estate — construction | Commercial Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,919	1,558
Credit cards | Commercial Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	132	144
Credit cards | Consumer Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	974	1,130
Commercial real estate loans | Commercial Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	15,384	15,049
Commercial lease financing | Commercial Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	4,524	4,688
Real estate — residential mortgage | Consumer Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	8,149	7,023
Home equity loans | Consumer Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	9,782	10,274
Residential - Prime Loans | Consumer Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	17,931	17,297
Consumer direct loans | Consumer Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	4,327	3,513
Credit cards | Consumer Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	974	1,130
Consumer indirect loans | Consumer Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	4,722	4,674
Collateral pledged | Commercial Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	18	15
Education Lending | Discontinued operations
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 780	$ 865