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