Additional Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash paid during the year for:
Interest	$ 7,668	$ 7,421	$ 10,568
Income taxes	99,754	88,277	104,324
Non-cash financing activities:
Assets acquired under capital lease obligations	$ 3,847	$ 93	$ 414