Statement Of Cash Flow Information (Non-Cash Additions and Non-Cash Revenue) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Nonmonetary Transaction [Line Items]
Non-monetary exchanges related to resale licensing revenue			$ 1,293	$ 6,871
Non-monetary exchanges from underwriting of new data acquisition			4,122	3,202
Other non-monetary exchanges			0	188
Completion of data in progress from prior non-monetary exchanges			142	0
Less: Non-monetary exchanges for data in progress			(2,442)	(142)
Total non-cash additions to seismic data library			3,115	10,119
Non-cash revenue			6,175	7,897
Underwriting [Member]
Nonmonetary Transaction [Line Items]
Non-cash revenue	1,645	931	3,273	2,314
Specific Data Licenses and Selections [Member]
Nonmonetary Transaction [Line Items]
Non-cash revenue	1,849	2,481	2,882	5,514
Solutions [Member]
Nonmonetary Transaction [Line Items]
Non-cash revenue	$ 0	$ 69	$ 20	$ 69