Leases (Lease Cost) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Finance lease cost
Sublease income	$ (30)	$ (37)	$ (64)	$ (72)
Net lease cost	72	66	144	139
Short-term lease, cost	27	29	58	63
Cost of equipment rentals, excluding depreciation
Lessee, Lease, Description [Line Items]
Operating lease cost	86	86	178	175
Selling, general and administrative expenses
Lessee, Lease, Description [Line Items]
Operating lease cost	3	2	6	5
Restructuring charge
Lessee, Lease, Description [Line Items]
Operating lease cost	1	7	2	13
Depreciation of rental equipment
Finance lease cost
Amortization of leased assets	8	7	15	14
Non-rental depreciation and amortization
Finance lease cost
Amortization of leased assets	1	0	1	1
Interest expense, net
Finance lease cost
Interest on lease liabilities	$ 3	$ 1	$ 6	$ 3