Long-term and Short-term Debt - Summary of Long-term Debt Instruments (Tables)

6 Months Ended

Mar. 31, 2020

Debt Disclosure [Abstract]

Schedule of Long-term Debt Instruments

	March 31, 2020			September 30, 2019
2.050% notes, payable in March 2020	$	—		$	299.4
2.875% notes, payable in March 2025	321.0			307.6
6.70% debentures, payable in January 2028	250.0			250.0
3.500% notes, payable in March 2029	425.0			425.0
6.25% debentures, payable in December 2037	250.0			250.0
4.200% notes, payable in March 2049	575.0			575.0
5.20% debentures, payable in January 2098	200.0			200.0
Unamortized discount and other	(50.8		)	(50.1		)
Total	1,970.2			2,256.9
Less current portion	—			(300.5		)
Long-term debt	$	1,970.2		$	1,956.4