Property Plant and Equipment (Detail) (USD $)	12 Months Ended
	Sep. 30, 2014		Sep. 30, 2013
Property, Plant and Equipment [Line Items]
Property, plant and equipment	337,922,000		$ 325,464,000
Less accumulated depreciation	(173,428,000)		(152,231,000)
Net property, plant and equipment	164,494,000		173,233,000
Land, building and other
Property, Plant and Equipment [Line Items]
Property, plant and equipment	13,848,000		10,822,000
Recording Equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment	206,517,000		197,134,000
Line Clearing Equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment	1,084,000		937,000
Vibrator Energy Sources
Property, Plant and Equipment [Line Items]
Property, plant and equipment	78,119,000		80,309,000
Vehicles
Property, Plant and Equipment [Line Items]
Property, plant and equipment	36,730,000		35,623,000
Other
Property, Plant and Equipment [Line Items]
Property, plant and equipment	1,624,000	[1]	$ 639,000	[1]
Minimum | Land, building and other
Property, Plant and Equipment [Line Items]
Useful Lives	3 years
Minimum | Recording Equipment
Property, Plant and Equipment [Line Items]
Useful Lives	5 years
Minimum | Line Clearing Equipment
Property, Plant and Equipment [Line Items]
Useful Lives	5 years
Minimum | Vibrator Energy Sources
Property, Plant and Equipment [Line Items]
Useful Lives	5 years
Minimum | Vehicles
Property, Plant and Equipment [Line Items]
Useful Lives	1 year 6 months
Maximum | Land, building and other
Property, Plant and Equipment [Line Items]
Useful Lives	40 years
Maximum | Recording Equipment
Property, Plant and Equipment [Line Items]
Useful Lives	10 years
Maximum | Vibrator Energy Sources
Property, Plant and Equipment [Line Items]
Useful Lives	15 years
Maximum | Vehicles
Property, Plant and Equipment [Line Items]
Useful Lives	10 years

[1] Other represents accumulated costs associated with equipment fabrication and modification not yet completed.