Lease Obligations - Lessee - Lease Assets and Lease Liabilities (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Lessee Lease Description [Line Items]
Operating lease right-of-use assets	$ 473,000,000	$ 0
Total right-of-use assets	507,000,000
Operating lease liabilities	555,000,000
Finance lease liabilities	35,000,000
Total lease liabilities	590,000,000
Finance lease right of use asset accumulated amortization	27,000,000
Operating lease right of use asset accumulated amortization	75,000,000
Other assets
Lessee Lease Description [Line Items]
Operating lease right-of-use assets	473,000,000
Bank premises and equipment
Lessee Lease Description [Line Items]
Finance lease right-of-use assets	34,000,000
Accrued taxes, interest and expenses
Lessee Lease Description [Line Items]
Operating lease liabilities	555,000,000
Long-term debt
Lessee Lease Description [Line Items]
Finance lease liabilities	$ 35,000,000