Leases (Lease Cost) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Finance lease cost
Sublease income	$ (42)	$ (30)	$ (74)	$ (64)
Net lease cost	71	72	140	144
Short-term lease, cost	34	27	62	58
Cost of equipment rentals, excluding depreciation
Lessee, Lease, Description [Line Items]
Operating lease cost	100	86	190	178
Selling, general and administrative expenses
Lessee, Lease, Description [Line Items]
Operating lease cost	3	3	5	6
Restructuring charge
Lessee, Lease, Description [Line Items]
Operating lease cost	0	1	1	2
Depreciation of rental equipment
Finance lease cost
Amortization of leased assets	8	8	15	15
Non-rental depreciation and amortization
Finance lease cost
Amortization of leased assets	1	1	1	1
Interest expense, net
Finance lease cost
Interest on lease liabilities	$ 1	$ 3	$ 2	$ 6