Disclosures About Derivative Instruments and Hedging Activities (Details Textual) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Dec. 31, 2012 gal Agreement	Dec. 31, 2011 gal
Disclosures About Derivative Instruments, Hedging Activities and Financial Instruments (Textual) [Abstract]
Maximum Length of Time Hedged in Price Risk Cash Flow Hedge (in months)	23 months
Weighted Average Length of Time Hedge in Price Risk Cash Flow Hedge (in months)	5 months
Derivative, Nonmonetary Notional Amount	200,300,000	125,400,000
Net losses associated with commodity price risk hedges expected to be reclassified into earnings during the next twelve months	$ 31,611
Number of settled or unsettled interest rate protection agreements outstanding (in agreements)	0