Leases (Lease Cost) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Finance lease cost
Sublease income	$ (41)	$ (42)	$ (105)	$ (114)
Net lease cost	68	67	212	206
Short-term lease, cost	32	40	90	103
Cost of equipment rentals, excluding depreciation
Lessee, Lease, Description [Line Items]
Operating lease cost	95	95	273	270
Selling, general and administrative expenses
Lessee, Lease, Description [Line Items]
Operating lease cost	2	3	8	8
Restructuring charge
Lessee, Lease, Description [Line Items]
Operating lease cost	1	1	3	14
Depreciation of rental equipment
Finance lease cost
Amortization of leased assets	8	7	23	21
Non-rental depreciation and amortization
Finance lease cost
Amortization of leased assets	0	1	1	2
Interest expense, net
Finance lease cost
Interest on lease liabilities	$ 3	$ 2	$ 9	$ 5