Leases (Lease Cost) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Finance lease cost
Sublease income	$ (42)	$ (114)
Net lease cost	67	206
Cost of equipment rentals, excluding depreciation
Lessee, Lease, Description [Line Items]
Operating lease cost	95	270
Selling, general and administrative expenses
Lessee, Lease, Description [Line Items]
Operating lease cost	3	8
Restructuring charge
Lessee, Lease, Description [Line Items]
Operating lease cost	1	14
Depreciation of rental equipment
Finance lease cost
Amortization of leased assets	7	21
Non-rental depreciation and amortization
Finance lease cost
Amortization of leased assets	1	2
Interest expense, net
Finance lease cost
Interest on lease liabilities	$ 2	$ 5