Capitalization (Details) (USD $)	9 Months Ended			0 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Sep. 30, 2012 5.25% Notes Due in March 2013	Feb. 15, 2013 3.75% Notes Due In March 1, 2023 [Member]
Debt Instrument [Line Items]
Common stock shares issued due to stock option exercises	457,091
Issue shares of common stock for the Direct Stock Purchase and Dividend Reinvestment Plan	97,554
Common stock issued	12,380
Shares tendered	309,307
Current portion of long-term debt			$ 250,000,000
Long-term debt, face value				500,000,000
Long-term debt, interest rate			5.25%	3.75%
Percentage of principal amount				101.00%
Net proceeds from issuance of long-term debt	$ 495,415,000	$ 496,085,000		$ 495,400,000