Summary of Company's Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Segment Reporting Information [Line Items]
Revenues	$ 26,285	$ 40,728	$ 68,551	$ 101,348	$ 68,288	$ 78,148	$ 76,420	$ 77,751	$ 236,912	$ 300,607	$ 191,664
Income (loss) from operations	(3,282)	5,458	15,956	35,667	19,132	24,991	25,556	31,548	53,799	101,227	50,865
Depreciation, amortization and stock-based compensation expenses									21,893	12,773	10,349
Interest income									123	880	743
Interest expense									471	260	199
Seismic
Segment Reporting Information [Line Items]
Revenues									214,946	275,201	164,921
Income (loss) from operations									65,159	110,118	55,990
Depreciation, amortization and stock-based compensation expenses									19,925	11,207	8,533
Interest income									74	781	581
Interest expense									0	141	199
Non-Seismic
Segment Reporting Information [Line Items]
Revenues									21,420	24,578	25,942
Income (loss) from operations									2,733	3,344	4,479
Depreciation, amortization and stock-based compensation expenses									468	289	320
Interest income									5	2	5
Interest expense									0	0	0
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Revenues									546	828	801
Income (loss) from operations									(14,093)	(12,235)	(9,604)
Depreciation, amortization and stock-based compensation expenses									1,500	1,277	1,496
Interest income									44	97	157
Interest expense									$ 471	$ 119	$ 0