Acquisitions (Details Textual) (USD $)	3 Months Ended								12 Months Ended					12 Months Ended					12 Months Ended				12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Hill Hire [Member]	Jun. 08, 2011 Hill Hire [Member] Vehicle Trailer Person Lease	Dec. 31, 2011 Other Acquisitions [Member]	Dec. 31, 2010 Other Acquisitions [Member]	Dec. 31, 2009 Other Acquisitions [Member]	Dec. 31, 2011 Total Logistic Control [Member]	Dec. 31, 2010 Total Logistic Control [Member]	Dec. 31, 2011 Edart Leasing LLC Acquisition [Member] Trailer	Dec. 31, 2010 Edart Leasing LLC Acquisition [Member]	Dec. 31, 2009 Edart Leasing LLC Acquisition [Member]	Feb. 02, 2009 Edart Leasing LLC Acquisition [Member] Person Vehicle	Dec. 31, 2011 All 2011 Acquisitions [Member]
Acquisitions (Textual) [Abstract]
Purchase price of acquisitions													$ 251,495,000	$ 114,000,000			$ 207,123,000					$ 85,000,000
Number of full service lease vehicles													8,000
Number of rental vehicles													5,700									1,600
Number of contractual customers acquired													400									340
Transaction costs related to the acquisition												2,000,000						4,000,000
Number of trailers included in fleet													9,700
Number of vehicles acquired for remarketing																			525
Goodwill														28,000,000				131,911,000
Customer relationship intangibles														12,000,000
Acquisitions									(361,921,000)	(211,897,000)	(88,873,000)	251,000,000		106,800,000	5,000,000	8,000,000	2,600,000		1,000,000	2,000,000	81,000,000
Revenue	1,541,094,000	1,570,720,000	1,513,344,000	1,425,376,000	1,313,426,000	1,316,948,000	1,286,123,000	1,219,938,000	6,050,534,000	5,136,435,000	4,887,254,000												473,000,000
Net earnings	48,095,000	56,524,000	40,033,000	25,125,000	37,121,000	38,835,000	29,841,000	12,373,000	169,777,000	118,170,000	61,945,000												42,000,000
Reduction in purchase price due to contractual adjustments																	$ 1,000,000