Supplemental Cash Flow Information and Non-Cash Activity (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash paid during the period for:
Interest	$ 206	$ 154
Income taxes (refunds)	819	(762)
Non-cash items from investing and financing activities:
Investment in multi-client data library financed through accounts payable	1,654	3,885
Purchases of property, plant, and equipment financed through accounts payable	$ 730	$ 179