Leases - 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	$ 39	$ 28
Operating cash flows from finance leases	3	0
Financing cash flows from finance leases	59	5
Right-of-use assets obtained in exchange for lease liabilities:
Operating leases	0	24
Finance leases	$ 293	$ 9