Lease Obligations - Lessee - Lease Costs (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Lease Cost [Line Items]
Total finance lease costs	$ 2	$ 3
Total operating lease costs	32	61
Total lease costs	34	64
Right of use asset impairment	7	7
Net occupancy and equipment expense
Lease Cost [Line Items]
Amortization of right-of-use assets	2	3
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	47
Short-term lease cost	0	0
Variable lease cost	8	16
Sublease income	$ (1)	$ (2)