Leases (Lease Cost) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Finance lease cost
Sublease income	$ (32)	$ (34)
Net lease cost	69	72
Short-term lease, cost	28	31
Cost of equipment rentals, excluding depreciation
Lessee, Lease, Description [Line Items]
Operating lease cost	90	92
Selling, general and administrative expenses
Lessee, Lease, Description [Line Items]
Operating lease cost	2	3
Restructuring charge
Lessee, Lease, Description [Line Items]
Operating lease cost	1	1
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	0
Interest expense, net
Finance lease cost
Interest on lease liabilities	$ 1	$ 3