Supplemental Cash Flow Information and Non-Cash Activity (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Cash paid during the period for:
Interest	$ 8,149	$ 7,843
Income taxes (refunds)	(6)	9,649
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	6,706
Bond exchange	10,740	0
Transfer of inventory to property, plant, equipment and seismic rental equipment	$ 0	$ 15,936