Capitalization (Details) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended	12 Months Ended
	Jun. 30, 2011	Sep. 30, 2010
Common stock shares issued due to stock option exercises	1,044,970
Common stock shares issued for restricted stock awards	47,250
Original issue of shares of common stock	11,250
Common stock tendered	503,262
Current Portion of long-term debt	$ 150,000	$ 200,000
Medium-term notes maturity date	Nov. 01, 2011	Nov. 01, 2010
Direct Stock Purchase And Dividend Reinvestment Plan [Member]
Stock issued during the period shares	24,499
7.5% Notes [Member]
Interest rate on medium-term notes		7.50%
6.7% Medium-Term Notes [Member]
Current Portion of long-term debt	$ 150,000
Interest rate on medium-term notes	6.70%