Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Supplemental disclosures:
Interest paid	$ 0	$ 0	$ 0
Income taxes paid, net	27,353	24,125	26,456
Non-cash investing and financing activities:
Non-cash capital expenditures	$ 270	$ 83	$ (79)