Leases (Lease Cost) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Finance lease cost
Sublease income	$ (61)	$ (41)	$ (135)	$ (105)
Net lease cost	71	68	211	212
Short-term lease, cost	50	32	112	90
Cost of equipment rentals, excluding depreciation
Lessee, Lease, Description [Line Items]
Operating lease cost	119	95	309	273
Selling, general and administrative expenses
Lessee, Lease, Description [Line Items]
Operating lease cost	3	2	8	8
Restructuring charge
Lessee, Lease, Description [Line Items]
Operating lease cost	0	1	1	3
Depreciation of rental equipment
Finance lease cost
Amortization of leased assets	9	8	24	23
Non-rental depreciation and amortization
Finance lease cost
Amortization of leased assets	0	0	1	1
Interest expense, net
Finance lease cost
Interest on lease liabilities	$ 1	$ 3	$ 3	$ 9