Financial Instruments and Fair Value Measurements (Estimated Fair Values of Financial Instruments) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Sep. 30, 2014
Notes receivable from municipalities, Carrying Cost	$ 15,638	$ 15,228
Short-term borrowings, Carrying Cost	(2,430)	0
Long-term debt, including current portion, Carrying Cost	(850,000)	(710,000)
Fair Value, Inputs, Level 2 [Member]
Notes receivable from municipalities, Estimated Fair Value	16,112	15,988
Short-term borrowings, Estimated Fair Value	(2,430)	0
Long-term debt, including current portion, Estimated Fair Value	$ (873,734)	$ (752,513)