Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Supplemental Cash Flow Elements [Abstract]
Interest paid	$ 143,990	$ 144,973	$ 139,595
Income taxes paid	14,062	13,379	11,382
Changes in accounts payable related to purchases of revenue earning equipment	(142,256)	28,134	39,071
Operating and revenue earning equipment acquired under capital leases	$ 1,230	$ 5,959	$ 7,972