Derivatives (Effect of derivatives on consolidated statements of income) (Details) gal in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016 USD ($) gal	Sep. 30, 2015 USD ($) gal	Sep. 30, 2016 USD ($) gal	Sep. 30, 2015 USD ($) gal
Fixed price swap contracts
Derivative Instruments, Gain (Loss) [Line Items]
Purchases of diesel covered by the fixed price swaps (in gallons) | gal	2.7	2.8	7.7	8.2
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	$ (1)	$ (2)	$ (5)	$ (5)
Amount of income (expense) recognized on hedged item	(6)	(7)	(17)	(23)
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	(4)	(5)	(1)	(5)
Amount of income (expense) recognized on hedged item	$ 4	$ 5	$ 1	$ 5