Debt (Tables)

12 Months Ended

Sep. 30, 2017

Debt Disclosure [Abstract]

Composition of Long-term Debt

Long-term debt comprises the following at September 30:

	2017			2016
Senior Notes:
4.12%, due September 2046	$	200,000		$	200,000
4.98%, due March 2044	175,000			175,000
4.12%, due October 2046	100,000			—
6.21%, due September 2036	100,000			100,000
2.95%, due June 2026	100,000			100,000
Medium-Term Notes:
6.17%, due June 2017	—			20,000
7.25%, due November 2017	20,000			20,000
5.67%, due January 2018	20,000			20,000
6.50%, due August 2033	20,000			20,000
6.13%, due October 2034	20,000			20,000
Total long-term debt	755,000			675,000
Less: unamortized debt issuance costs	(3,899		)	(3,559		)
Less: current maturities	(39,996		)	(19,986		)
Total long-term debt due after one year	$	711,105		$	651,455