Derivatives (Effect of derivatives on consolidated statements of income) (Details) gal in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($) gal	Jun. 30, 2016 USD ($) gal	Jun. 30, 2017 USD ($) gal	Jun. 30, 2016 USD ($) gal
Fixed price swap contracts
Derivative Instruments, Gain (Loss) [Line Items]
Purchases of diesel covered by the fixed price swaps (in gallons) | gal	1.9	2.4	3.8	5.0
Fixed price swap contracts | Designated as hedging instruments | Other income (expense), net
Derivative Instruments, Gain (Loss) [Line Items]
Amount of income (expense) recognized on derivative	$ 0	$ 0	$ 0	$ 0
Fixed price swap contracts | Designated as hedging instruments | Cost of equipment rentals, excluding depreciation
Derivative Instruments, Gain (Loss) [Line Items]
Amount of income (expense) recognized on derivative	0	(2)	0	(4)
Amount of income (expense) recognized on hedged item	(5)	(6)	(10)	(11)
Foreign currency forward contracts | Not designated as hedging instruments | Other income (expense), net
Derivative Instruments, Gain (Loss) [Line Items]
Amount of income (expense) recognized on derivative	7	3	7	3
Amount of income (expense) recognized on hedged item	$ (7)	$ (3)	$ (7)	$ (3)