Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Supplemental disclosure:
Interest paid	$ 0	$ 0	$ 0	$ 0
Income taxes paid	8,551	6,321	19,398	17,167
Non-cash investing and financing activities:
Non-cash capital expenditures	$ (1,211)	$ (17)	$ 101	$ (190)