Fair Value Measurements (Details) (Commodity Contract [Member], Fair Value, Measurements, Recurring [Member], USD $) In Thousands	Sep. 30, 2011	Sep. 30, 2010
Assets:
Derivative Assets	$ 864	$ 8,025
Liabilities:
Derivative financial instruments, liabilities	(7,248)
Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1) [Member]
Assets:
Derivative Assets	0	0
Liabilities:
Derivative financial instruments, liabilities	0
Significant Other Observable Inputs (Level 2) [Member]
Assets:
Derivative Assets	864	8,025
Liabilities:
Derivative financial instruments, liabilities	(7,248)
Unobservable Inputs (Level 3) [Member]
Assets:
Derivative Assets	0	0
Liabilities:
Derivative financial instruments, liabilities	$ 0