Oil and Gas Properties - Additional Information (Detail)	9 Months Ended
	Jun. 30, 2012 mi Well Property
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Lease period	15 years
Number of sections	68
Seismic line	25
Number of drill wells for future oil production	10
Undrilled Section
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Seismic line	2
Maximum
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Number of drill wells	68
Minimum
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Number of drill wells	44