Leasing - Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ 30	$ 32
Operating cash flows from finance leases	0	0
Financing cash flows from finance leases	3	0
Lease Assets Obtained in Exchange for Lease Obligations
Operating Leases	(2)	12
Finance Leases	$ 8	$ 1