Financial Instruments and Fair Value Measurements (Estimated Fair Values of Financial Instruments) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Sep. 30, 2012	Mar. 31, 2012	Sep. 30, 2011
Financial Instruments and Fair Value Measurments
Cash and cash equivalents, Estimated Fair Value	$ 54,658	$ 61,829
Investments in deferred compensation program, Estimated Fair Value	8,280	7,316
Note receivable from municipality, Estimated Fair Value	2,621
Short-term borrowings, Estimated Fair Value	(5,086)	(329)
Long-term debt, including current portion, Estimated Fair Value	(595,779)	(443,827)
Cash and cash equivalents, Carrying Cost	54,658	61,829	56,329	74,539
Investments in deferred compensation program, Carrying Cost	8,280	7,316
Note receivable from municipality, Carrying Cost	2,064
Short-term borrowings, Carrying Cost	(5,086)	(329)
Long-term debt, including current portion, Carrying Cost	$ (550,000)	$ (391,875)