STATEMENTS OF CAPITALIZATION (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Sep. 30, 2011
Common Stock Equity:
Common stock, par value $1 per share and Paid-in Capital: Authorized - 2012 and 2011, 50,000,000 shares; Issued - 2012, 12,804 shares; and 2011, 11,717 shares	$ 257,415	$ 212,970
Retained earnings	236,014	223,460
Accumulated other comprehensive loss	(2,101)	(2,473)
Total Common Stock Equity	491,328	433,957
Long-Term Debt:
Debt instrument, principal outstanding	340,000	365,000
Unamortized discount, net of premium, on long-term debt	(584)	(643)
Total Long-Term Debt	339,416	364,357
Total Capitalization	830,744	798,314
First Mortgage Bonds Series, due October 15, 2012 [Member]
Long-Term Debt:
Debt instrument, principal outstanding	0	25,000
First Mortgage Bonds Series, due May 1, 2019 [Member]
Long-Term Debt:
Debt instrument, principal outstanding	50,000	50,000
First Mortgage Bonds Series, due June 1, 2029 [Member]
Long-Term Debt:
Debt instrument, principal outstanding	25,000	25,000
First Mortgage Bonds Series, due September 15, 2030 [Member]
Long-Term Debt:
Debt instrument, principal outstanding	30,000	30,000
First Mortgage Bonds Series, due May 1, 2034 [Member]
Long-Term Debt:
Debt instrument, principal outstanding	100,000	100,000
First Mortgage Bonds Series, due June 1, 2036 [Member]
Long-Term Debt:
Debt instrument, principal outstanding	55,000	55,000
First Mortgage Bonds Series, due October 15, 2038 [Member]
Long-Term Debt:
Debt instrument, principal outstanding	$ 80,000	$ 80,000