Supplemental Cash Flow Information and Non-cash Activity (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Supplemental disclosure of cash flow information is as follows:
Interest paid	$ 4,625	$ 6,440	$ 11,798
Income taxes paid	18,146	15,473	7,263
Non-cash items from investing and financing activities is as follows:
Transfer of inventory to rental equipment	6,737	2,978	3,606
Purchase of computer equipment financed through capital leases	4,647	2,597	555
Sale of rental equipment financed with a note receivables	0	3,578	0
Exchange of receivable related to a business acquisition	0	2,000	0
Reduction in multi-client data library related to finalization of accrued liabilities	0	1,888	0
Expiration of BGP warrant	0	0	32,001
Conversion of BGP Domestic Convertible Note to equity	0	0	28,571
Investment in INOVA Geophysical	0	0	119,000
Exchange of Reservoir Exploration Technology receivables into shares	0	0	9,516
Investment in multi-client data library financed through trade payables	$ 0	$ 0	$ 3,429