Capitalization (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Dec. 31, 2012	Dec. 31, 2012 Direct Stock Purchase And Dividend Reinvestment Plan [Member]	Dec. 31, 2012 5.25% Notes Due in March 2013	Sep. 30, 2012 5.25% Notes Due in March 2013
Debt Instrument [Line Items]
Common stock shares issued due to stock option exercises	342,822
Issue shares of common stock for the Direct Stock Purchase and Dividend Reinvestment Plan		60,631
Common stock issued	4,050
Shares tendered	255,518
Current portion of long-term debt			$ 250	$ 250
Long-term debt, interest rate			5.25%	5.25%