Supplemental Cash Flow Information (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Business Acquisition [Line Items]
Interest paid	$ 139,595,000	$ 132,946,000	$ 126,764,000
Income taxes paid	11,382,000	13,063,000	11,613,000
Changes in accounts payable related to purchases of revenue earning equipment	39,071,000	43,745,000	27,528,000
Operating and revenue earning equipment acquired under capital leases	7,972,000	5,698,000	20,670,000
Fair value of debt assumed on acquisition	0	0	379,000
Capital leases assumed			20,000,000
Payments to acquire businesses	(9,972,000)	(1,858,000)	(5,113,000)
Payments made related to prior year acquisitions [Member]
Business Acquisition [Line Items]
Payments to acquire businesses	$ (1,858,000)