Leasing - Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ 31	$ 38	$ 61	$ 70
Operating cash flows from finance leases	1	0	1	0
Financing cash flows from finance leases	3	0	6	0
Lease Assets Obtained in Exchange for Lease Obligations
Operating Leases	4	8	2	20
Finance Leases	$ 7	$ 8	$ 15	$ 9