Statement of Cash Flow Information - Non-Cash Additions and Non-Cash Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Nonmonetary Transaction
Non-monetary exchanges related to resale licensing revenue			$ 1,210	$ 1,250
Non-monetary exchanges related to data processing and reproduction services			152	0
Total non-cash additions to seismic data library			1,362	1,250
Non-cash revenue			1,837	1,554
Acquisition revenue on underwriting [Member]
Nonmonetary Transaction
Non-cash revenue	$ 0	$ 103	0	229
Licensing revenue from specific data licenses and selections [Member]
Nonmonetary Transaction
Non-cash revenue	1,322	0	1,385	1,250
Solutions and other revenue recognized [Member]
Nonmonetary Transaction
Non-cash revenue	$ 418	$ 44	$ 452	$ 75