Acquisitions (Consideration Transferred) (Details) (RSC [Member], USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended
	Apr. 30, 2012
Business Acquisition [Line Items]
Cash consideration	$ 1,161
Total purchase consideration	2,586
Option exchange ratio, component one (ratio)	0.2783
Option exchange ratio, component two (ratio)	10.8
Share transaction trading period	10 days
Option exchange ratio (ratio)	0.5161
Stock consideration [Member]
Business Acquisition [Line Items]
Share consideration	1,396
Number of shares issued for acquisition (in shares)	30,000,000
Share-based compensation awards [Member]
Business Acquisition [Line Items]
Share consideration	$ 29	[1]

[1] This relates to RSC stock options and restricted stock units which were outstanding as of the acquisition date. Each RSC stock option was converted into an adjusted United Rentals stock option to acquire a number of shares of United Rentals common stock, determined by multiplying the number of shares of RSC common stock subject to the RSC stock option by the option exchange ratio (rounded down, if necessary, to a whole share of United Rentals common stock). The “option exchange ratio” means the sum of (i) 0.2783 and (ii) the quotient determined by dividing $10.80 by the volume-weighted average of the closing sale prices of shares of URI common stock as reported on the NYSE composite transactions reporting system for each of the 10 consecutive trading days ending with the acquisition date. The option exchange ratio was 0.5161. The exercise price per share of United Rentals common stock subject to the adjusted United Rentals option is equal to the per share exercise price of such RSC stock option divided by the option exchange ratio (rounded up, if necessary, to the nearest whole cent). Each RSC restricted stock unit (other than an award held by a member of the RSC board who was not also an employee or officer of RSC at such time) was converted into an adjusted United Rentals restricted stock unit in an amount determined by multiplying the number of shares of RSC common stock subject to the RSC restricted stock unit by the option exchange ratio. The portion of the United Rentals replacement awards that has been included in the purchase consideration was calculated as $29 and is based on the vesting which occurred prior to the acquisition date.