Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Supplemental Cash Flow Information
Income taxes paid, net of refunds	$ 63,899	$ 57,728	$ 65,511
Interest paid	6,181	3,389	2,264
Assets acquired through capital leases	$ 4,212	$ 2,810	$ 29,739