Revenue Recognition (Revenue from Non-Monetary Exchanges) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Nonmonetary Transaction
Seismic data library additions	$ 250	$ 222
Non-cash revenue	289	1
Specific Data Licenses or Selections of Data [Member]
Nonmonetary Transaction
Non-cash revenue	250	0
Acquisition Contracts [Member]
Nonmonetary Transaction
Non-cash revenue	39	1
Seismic Data Library [Member]
Nonmonetary Transaction
Seismic data library additions	$ 250	$ 222