Commitments and Contingencies (Details Textual) (USD $) In Thousands, unless otherwise specified	1 Months Ended	3 Months Ended	9 Months Ended		12 Months Ended	24 Months Ended
	Jun. 30, 2011	Jun. 30, 2011	Jun. 30, 2012 gal	Jun. 30, 2011	Sep. 30, 2009	Sep. 30, 2006	Sep. 30, 2011
Site Contingency [Line Items]
Environmental Remediation Charges	$ 6,000	$ 6,000		$ 6,000	$ 13,700	$ 26,000
Commitment And Contingencies (Textual) [Abstract]
Period to publish a proposed regulation			24 months
Period to publicize a final regulation			18 months
Period of ground water investigation. minimum			6 years
Extension of remediation project, minimum			50 years
Estimated increase in capital cost of expansion project	6,400
Estimate cost of O&M	400
Increase in annual O&M cost	1,900
Estimated project life	4 years
Measurement for new ground water extraction wells			450
Measurement for existing wells			750
Estimated life of project, minimum			5 years
Estimated life of project, maximum			18 years
More likely estimated life of project, minimum			7 years
More likely estimated life of project, maximum			14 years
Amount accrued through estimated life of the project			20,253				26,173
Maturity life of the project			2019
Minimum [Member]
Site Contingency [Line Items]
Environmental Remediation Charges			16,600
Maximum [Member]
Site Contingency [Line Items]
Environmental Remediation Charges			$ 39,900