Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Supplemental cash flow information
Interest paid	$ 69,681	$ 69,834
Income taxes paid	9,970	7,332
Changes in accounts payable related to purchases of revenue earning equipment	124,766	1,520
Operating and revenue earning equipment acquired under capital leases	5,847	2,371
Acquisition payments	$ 0	$ 1,649