Supplemental Cash Flow Information and Non-Cash Activity (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Cash paid during the period for:
Interest	$ 8,819	$ 8,036
Income taxes	2,579	7,614
Non-cash items from investing and financing activities:
Purchases of computer equipment financed through capital leases	0	1,178
Investment in multi-client data library financed through accounts payable	0	13,617
Bond exchange	10,740	0
Transfer of inventory to property, plant, equipment and seismic rental equipment	$ 0	$ 15,936