Company's Segment Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013	Mar. 31, 2012
Segment Reporting Information [Line Items]
Net sales	$ 76,420	$ 56,233	$ 154,171	$ 99,514
Total income (loss) from operations	25,556	16,472	57,104	29,070
Seismic
Segment Reporting Information [Line Items]
Net sales	69,758	48,716	141,842	86,008
Total income (loss) from operations	27,842	17,716	61,803	31,677
Non Seismic
Segment Reporting Information [Line Items]
Net sales	6,444	7,317	11,911	13,105
Total income (loss) from operations	892	1,326	1,357	2,319
Corporate
Segment Reporting Information [Line Items]
Net sales	218	200	418	401
Total income (loss) from operations	$ (3,178)	$ (2,570)	$ (6,056)	$ (4,926)