Lease Obligations - Lessee - Lease Costs (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Lease Cost [Line Items]
Total finance lease costs	$ 2	$ 5
Total operating lease costs	31	92
Total lease costs	33	97
Right of use asset, operating lease impairment	5	12
Net occupancy and equipment expense
Lease Cost [Line Items]
Amortization of right-of-use assets	2	5
Interest Expense, Long-Term Debt
Lease Cost [Line Items]
Interest on lease liabilities	0	0
Net occupancy expense
Lease Cost [Line Items]
Operating lease cost	25	72
Short-term lease cost	0	0
Variable lease cost	7	23
Sublease income	$ (1)	$ (3)