Summary of Company's Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Segment Reporting Information [Line Items]
Revenues	$ 40,728	$ 78,148	$ 210,627	$ 232,319
Income (loss) from operations	5,458	24,991	57,081	82,095
Seismic
Segment Reporting Information [Line Items]
Revenues	35,377	71,261	194,307	213,103
Income (loss) from operations	8,149	26,932	66,165	88,735
Non-Seismic
Segment Reporting Information [Line Items]
Revenues	5,209	6,683	15,916	18,594
Income (loss) from operations	777	972	1,814	2,329
Corporate
Segment Reporting Information [Line Items]
Revenues	142	204	404	622
Income (loss) from operations	$ (3,468)	$ (2,913)	$ (10,898)	$ (8,969)