Leasing - Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ 32	$ 34	$ 93	$ 104
Operating cash flows from finance leases	0	0	1	0
Financing cash flows from finance leases	3	0	9	0
Lease Assets Obtained in Exchange for Lease Obligations
Operating Leases	12	9	14	29
Finance Leases	$ 1	$ 14	$ 16	$ 23