Valuation and Qualifying Accounts (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2011
Regulatory Asset [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
BEGINNING BALANCE	$ 71		$ 141		$ 212
ADDITIONS, CHARGED TO EXPENSE	(71)		(70)		(71)
OTHER	0	[1]	0	[1]	0	[1]
ENDING BALANCE	0		71		141
Allowance for Doubtful Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
BEGINNING BALANCE	4,797		4,612		2,993
ADDITIONS, CHARGED TO EXPENSE	2,627		3,932		4,865
OTHER	(2,094)	[1]	(3,747)	[1]	(3,246)	[1]
ENDING BALANCE	$ 5,330		$ 4,797		$ 4,612

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