Goodwill and Other Intangible Assets (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2012	Dec. 31, 2011
Goodwill
Balance at the beginning of the period	$ 1,113,100,000	$ 1,049,600,000
Accumulated impairment losses at the beginning of the period	(721,000,000)	(721,000,000)
Net goodwill, balance at the beginning of the period	392,094,000	328,600,000
Goodwill acquired during the period	76,800,000	65,400,000
Adjustments to previously recorded purchase price allocation	200,000	(1,000,000)
Other changes during the period	2,300,000	(900,000)
Total changes in goodwill	79,300,000	63,500,000
Balance at the end of the period	1,192,400,000	1,113,100,000
Accumulated impairment losses at the end of the period	(721,000,000)	(721,000,000)
Net goodwill, balance at the end of the period	471,430,000	392,094,000
Car Rental
Goodwill
Balance at the beginning of the period	419,300,000	367,900,000
Accumulated impairment losses at the beginning of the period	(46,100,000)	(46,100,000)
Net goodwill, balance at the beginning of the period	373,200,000	321,800,000
Goodwill acquired during the period		53,100,000
Adjustments to previously recorded purchase price allocation	200,000	(900,000)
Other changes during the period	2,200,000	(800,000)
Total changes in goodwill	2,400,000	51,400,000
Balance at the end of the period	421,700,000	419,300,000
Accumulated impairment losses at the end of the period	(46,100,000)	(46,100,000)
Net goodwill, balance at the end of the period	375,600,000	373,200,000
Equipment Rental
Goodwill
Balance at the beginning of the period	693,800,000	681,700,000
Accumulated impairment losses at the beginning of the period	(674,900,000)	(674,900,000)
Net goodwill, balance at the beginning of the period	18,900,000	6,800,000
Goodwill acquired during the period	76,800,000	12,300,000
Adjustments to previously recorded purchase price allocation		(100,000)
Other changes during the period	100,000	(100,000)
Total changes in goodwill	76,900,000	12,100,000
Balance at the end of the period	770,700,000	693,800,000
Accumulated impairment losses at the end of the period	(674,900,000)	(674,900,000)
Net goodwill, balance at the end of the period	$ 95,800,000	$ 18,900,000