Lease Obligations - Lessee - Lease Assets and Lease Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2019	Jan. 01, 2019
Lessee Lease Description [Line Items]
Operating lease right-of-use assets		$ 509
Total right-of-use assets	$ 467
Operating lease liabilities	535
Finance lease liabilities	15
Total lease liabilities	550
Finance lease right of use asset accumulated amortization	37
Operating lease right of use asset accumulated amortization	23
Other assets
Lessee Lease Description [Line Items]
Operating lease right-of-use assets	452
Bank premises and equipment
Lessee Lease Description [Line Items]
Finance lease right-of-us assets	15
Accrued taxes, interest and expenses
Lessee Lease Description [Line Items]
Operating lease liabilities	535
Long-term debt
Lessee Lease Description [Line Items]
Finance lease liabilities	$ 15