Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Supplemental Cash Flow Elements [Abstract]
Interest paid	$ 144,973	$ 139,595	$ 132,946
Income taxes paid	13,379	11,382	13,063
Changes in accounts payable related to purchases of revenue earning equipment	28,134	39,071	43,745
Operating and revenue earning equipment acquired under capital leases	$ 5,959	$ 7,972	$ 5,698