Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Supplemental disclosure:
Interest paid	$ 0	$ 0	$ 0	$ 5
Income taxes paid	1,116	2,500	1,510	9,183
Non-cash investing and financing activities:
Non-cash capital expenditures	$ (116)	$ 1,159	$ (280)	$ 288