Valuation and Qualifying Accounts (Details) (USD $) In Thousands	12 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2009
Allowance for Doubtful Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
BEGINNING BALANCE	$ 2,993		$ 6,064		$ 4,580
CHARGED TO EXPENSE	4,865		3,307		9,588
OTHER	(3,246)	[1]	(6,378)	[1]	(8,104)	[1]
ENDING BALANCE	4,612		2,993		6,064
Allowance, Regulatory Asset Reserve [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
BEGINNING BALANCE	212		282		102
CHARGED TO EXPENSE	(71)		(70)		0
OTHER	0	[1]	0	[1]	180	[1]
ENDING BALANCE	$ 141		$ 212		$ 282

[1] Uncollectible accounts written off, less recoveries and adjustments.