Lease Obligations - Lessee - Lease Costs (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Lease Cost [Line Items]
Total finance lease costs	$ 6	$ 2
Total operating lease costs	28	31
Total lease costs	34	33
Impairment losses and termination charges		2
Net occupancy and equipment expense
Lease Cost [Line Items]
Amortization of ROU assets	5	1
Interest on long-term debt
Lease Cost [Line Items]
Interest on lease liabilities	1	1
Net occupancy expense
Lease Cost [Line Items]
Operating lease cost	20	24
Short-term lease cost	1	1
Variable lease cost	8	7
Sublease income	$ (1)	$ (1)