Leases (Lease Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Sublease income	$ (142)	$ (157)
Net lease cost	280	275
Short-term lease, cost	124	142
Cost of equipment rentals, excluding depreciation
Lessee, Lease, Description [Line Items]
Operating lease cost	366	370
Selling, general and administrative expenses
Lessee, Lease, Description [Line Items]
Operating lease cost	10	10
Restructuring charge
Lessee, Lease, Description [Line Items]
Operating lease cost	9	16
Depreciation of rental equipment
Lessee, Lease, Description [Line Items]
Finance lease cost	31	28
Non-rental depreciation and amortization
Lessee, Lease, Description [Line Items]
Finance lease cost	1	2
Interest expense, net
Lessee, Lease, Description [Line Items]
Interest on lease liabilities	$ 5	$ 6