Lease Obligations - Lessee - Lease Assets and Lease Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2019	Jan. 01, 2019
Lessee Lease Description [Line Items]
Operating lease right-of-use assets		$ 509
Total right-of-use assets	$ 487
Operating lease liabilities	543
Finance lease liabilities	26
Total lease liabilities	569
Finance lease right of use asset accumulated amortization	25
Operating lease right of use asset accumulated amortization	57
Other assets
Lessee Lease Description [Line Items]
Operating lease right-of-use assets	462
Bank premises and equipment
Lessee Lease Description [Line Items]
Finance lease right-of-us assets	25
Accrued taxes, interest and expenses
Lessee Lease Description [Line Items]
Operating lease liabilities	543
Long-term debt
Lessee Lease Description [Line Items]
Finance lease liabilities	$ 26