Income Taxes (Narrative) (Details) (USD $)			9 Months Ended
	Jun. 30, 2011	Sep. 30, 2010	Jun. 30, 2011 Stock Options [Member]	Jun. 30, 2011 Deferred Income Taxes [Member]	Sep. 30, 2010 Deferred Income Taxes [Member]
Tax benefits included in paid-in-capital			$ 18,100,000
Taxes refundable to customers	70,343,000	69,585,000		70,300,000	69,600,000
Recoverable future taxes	$ 151,142,000	$ 149,712,000		$ 151,100,000	$ 149,700,000