Capitalization (Details) - USD ($) $ in Thousands	9 Months Ended
	Jun. 30, 2017	Sep. 30, 2016
Debt Instrument [Line Items]
Common stock shares issued due to stock option exercises	31,632
Issue shares of common stock for the Direct Stock Purchase and Dividend Reinvestment Plan	146,872
Issue shares of common stock for the 401(k) plans	78,327
Shares tendered	47,785
Current Portion of Long-Term Debt	$ 300,000	$ 0
Long-term debt, interest rate	6.50%
Restricted Stock Units [Member]
Debt Instrument [Line Items]
Common stock issued	79,530
Performance Shares [Member]
Debt Instrument [Line Items]
Common stock issued	43,484
Board Of Directors [Member]
Debt Instrument [Line Items]
Common stock issued	17,017