Supplemental Cash Flow Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Other Significant Noncash Transactions [Line Items]
Payments to Acquire Businesses, Net of Cash Acquired	$ 1,649	$ 1,420
Supplemental cash flow information
Interest Paid	41,180	45,425
Income taxes paid	1,534	3,721
Changes in accounts payable related to purchases of revenue earning equipment	16,918	29,381
Operating and revenue earning equipment acquired under capital leases	2,245	458
Other Acquisitions Completed in Prior Years [Member]
Other Significant Noncash Transactions [Line Items]
Payments to Acquire Businesses, Net of Cash Acquired	$ 1,600	$ 1,400