Summary of Company's Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Segment Reporting Information [Line Items]
Sales	$ 68,288	$ 78,148	$ 76,420	$ 77,751	$ 36,949	$ 55,201	$ 56,233	$ 43,281	$ 300,607	$ 191,664	$ 172,970
Total income (loss) from operations	19,132	24,991	25,556	31,548	6,194	15,601	16,472	12,598	101,227	50,865	44,405
Total depreciation, amortization and stock-based compensation expenses									12,773	10,349	7,783
Interest income									880	743	267
Total interest expense									260	199	43
Seismic
Segment Reporting Information [Line Items]
Sales									275,201	178,221	158,653
Total income (loss) from operations									110,118	59,455	53,477
Total depreciation, amortization and stock-based compensation expenses									11,207	8,533	5,990
Interest income									781	581	139
Total interest expense									141	199
Non Seismic
Segment Reporting Information [Line Items]
Sales									24,578	12,642	13,519
Total income (loss) from operations									3,344	1,014	(37)
Total depreciation, amortization and stock-based compensation expenses									289	320	345
Interest income									2	5
Total interest expense
Corporate
Segment Reporting Information [Line Items]
Sales									828	801	798
Total income (loss) from operations									(12,235)	(9,604)	(9,035)
Total depreciation, amortization and stock-based compensation expenses									1,277	1,496	1,448
Interest income									97	157	128
Total interest expense									$ 119		$ 43