Leases (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Operating leases:
Operating lease ROU assets	$ 514	$ 536
Accrued expenses and other current liabilities	165	166
Other non-current liabilities	445	465
Total operating lease liabilities	610	631
Finance leases:
Property and equipment, gross	113	110
Accumulated depreciation	(32)	(23)
Property and equipment, net	81	87
Short-term debt	25	27
Long-term debt	58	61
Total finance lease liabilities	$ 83	$ 88