Derivatives (Effect of derivatives on consolidated statements of income) (Details) gal in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) gal	Dec. 31, 2015 USD ($) gal	Dec. 31, 2014 USD ($) gal
Swap
Derivative Instruments, Gain (Loss) [Line Items]
Derivative purchases of underlying commodity (in gallons) | gal	10.1	10.6	10.5
Swap | Designated as hedging instrument | Cost of equipment rentals, excluding depreciation
Derivative Instruments, Gain (Loss) [Line Items]
Amount of income (expense) recognized on derivative	$ (6)	$ (7)
Amount of income (expense) recognized on hedged item	(23)	(29)	$ (40)
Foreign currency forward | Not designated as hedging instrument | Other income (expense), net
Derivative Instruments, Gain (Loss) [Line Items]
Amount of income (expense) recognized on derivative	(3)	(5)	(7)
Amount of income (expense) recognized on hedged item	$ 3	$ 5	$ 7