Derivative Instruments and Hedging Activities - Effects of Derivative Instruments on Consolidated Statements of Income and Changes in AOCI (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Cash Flow Hedging | Interest Rate Contracts
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in AOCI	$ 0	$ 25,898	$ (11,528)
Cash Flow Hedging | Interest Rate Contracts | Interest Expense
Derivative Instruments, Gain (Loss)
Gain (Loss) Reclassified from AOCI into Income	(2,679)	(805)	(1,847)
Derivatives Not Designated as Hedging Instruments | Commodity Contracts | Operating and Administrative Expenses/Other Income, Net
Derivative Instruments, Gain (Loss)
Gain Recognized in Income	$ 0	$ 45	$ 223