Statement Of Cash Flow Information (Non-Cash Additions and Non-Cash Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Nonmonetary Transaction
Non-monetary exchanges related to resale licensing revenue	$ 250	$ 222
Total non-cash additions to seismic data library	250	222
Non-cash revenue	289	1
Acquisition revenue on underwriting [Member]
Nonmonetary Transaction
Non-cash revenue	39	1
Licensing revenue from specific data licenses and selections [Member]
Nonmonetary Transaction
Non-cash revenue	$ 250	$ 0