Statement Of Cash Flow Information (Non-Cash Additions and Non-Cash Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Nonmonetary Transaction
Non-monetary exchanges related to resale licensing revenue			$ 1,250	$ 1,840
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	2,640
Non-cash revenue			1,554	2,713
Acquisition revenue on underwriting [Member]
Nonmonetary Transaction
Non-cash revenue	$ 103	$ 54	229	78
Licensing revenue from specific data licenses and selections [Member]
Nonmonetary Transaction
Non-cash revenue	0	1,295	1,250	2,635
Solutions and other revenue recognized [Member]
Nonmonetary Transaction
Non-cash revenue	$ 44	$ 0	$ 75	$ 0