Leases (Lease Cost) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Finance lease cost
Sublease income	$ (34)	$ (38)
Net lease cost	72	70
Short-term lease, cost	31	34
Cost of equipment rentals, excluding depreciation
Lessee, Lease, Description [Line Items]
Operating lease cost	92	89
Selling, general and administrative expenses
Lessee, Lease, Description [Line Items]
Operating lease cost	3	3
Restructuring charge
Lessee, Lease, Description [Line Items]
Operating lease cost	1	6
Depreciation of rental equipment
Finance lease cost
Amortization of leased assets	7	7
Non-rental depreciation and amortization
Finance lease cost
Amortization of leased assets	0	1
Interest expense, net
Finance lease cost
Interest on lease liabilities	$ 3	$ 2