Derivatives (Effect of derivatives on consolidated statements of income) (Details) - Fixed price swap contracts gal in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($) gal	Mar. 31, 2015 USD ($) gal
Derivative Instruments, Gain (Loss) [Line Items]
Purchases of diesel covered by the fixed price swaps (in gallons) | gal	2.6	2.6
Designated as hedging instruments | Cost of equipment rentals, excluding depreciation
Derivative Instruments, Gain (Loss) [Line Items]
Amount of income (expense) recognized on derivative	$ (2)	$ (2)
Amount of income (expense) recognized on hedged item	$ (5)	$ (7)