Statement Of Cash Flow Information (Non-Cash Additions and Non-Cash Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Nonmonetary Transaction
Non-monetary exchanges related to resale licensing revenue			$ 1,250	$ 222
Non-monetary exchanges from underwriting of new data acquisition			0	408
Non-monetary exchanges related to data processing and reproduction services			0	392
Total non-cash additions to seismic data library			1,250	1,022
Non-cash revenue			1,407	1,364
Acquisition revenue on underwriting [Member]
Nonmonetary Transaction
Non-cash revenue	$ 87	$ 23	126	24
Licensing revenue from specific data licenses and selections [Member]
Nonmonetary Transaction
Non-cash revenue	1,000	1,340	1,250	1,340
Solutions and other revenue recognized [Member]
Nonmonetary Transaction
Non-cash revenue	$ 31	$ 0	$ 31	$ 0