Loan Portfolio - Loans by Category (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 94,646	$ 89,552
Net loans	93,746	88,669
Discontinued Operations [Member] | Education Lending [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net loans	865	1,100
Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	68,032	66,310
Commercial Loans [Member] | Commercial, Financial and Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	48,295	45,753
Commercial Loans [Member] | Commercial Real Estate: Commercial Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	13,491	14,285
Commercial Loans [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,558	1,666
Commercial Loans [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	15,049	15,951
Commercial Loans [Member] | Commercial Lease Financing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	4,688	4,606
Collateral for secured borrowings	15	10
Commercial Loans [Member] | Commercial Credit Card [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	144	132
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	26,614	23,242
Consumer Loans [Member] | Real Estate - Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	7,023	5,513
Consumer Loans [Member] | Home Equity Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	10,274	11,142
Consumer Loans [Member] | Residential Prime Financing Receivables [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	17,297	16,655
Consumer Loans [Member] | Consumer Direct Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	3,513	1,809
Consumer Loans [Member] | Consumer Credit Card [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,130	1,144
Consumer Loans [Member] | Consumer Indirect Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 4,674	$ 3,634