Leases (Lease Cost) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Finance lease cost
Sublease income	$ (37)	$ (72)
Net lease cost	66	139
Cost of equipment rentals, excluding depreciation
Lessee, Lease, Description [Line Items]
Operating lease cost	86	175
Selling, general and administrative expenses
Lessee, Lease, Description [Line Items]
Operating lease cost	2	5
Restructuring charge
Lessee, Lease, Description [Line Items]
Operating lease cost	7	13
Depreciation of rental equipment
Finance lease cost
Amortization of leased assets	7	14
Non-rental depreciation and amortization
Finance lease cost
Amortization of leased assets	0	1
Interest expense, net
Finance lease cost
Interest on lease liabilities	$ 1	$ 3