Fair Value Measurement (Details) - Fair value measured on recurring basis - USD ($) $ in Millions		Mar. 31, 2018	Sep. 30, 2017
Assets:
SERP plan assets	[1]	$ 21.6	$ 21.7
Foreign currency exchange derivatives	[2]	0.6	0.5
Interest rate contracts	[3]		0.3
Liabilities:
Foreign currency exchange derivatives	[2]	0.8	1.2
Interest rate contracts	[3]		0.7
Level 1
Assets:
SERP plan assets	[1]	21.6	21.7
Foreign currency exchange derivatives	[2]	0.0	0.0
Interest rate contracts	[3]		0.0
Liabilities:
Foreign currency exchange derivatives	[2]	0.0	0.0
Interest rate contracts	[3]		0.0
Level 2
Assets:
SERP plan assets	[1]	0.0	0.0
Foreign currency exchange derivatives	[2]	0.6	0.5
Interest rate contracts	[3]		0.3
Liabilities:
Foreign currency exchange derivatives	[2]	0.8	1.2
Interest rate contracts	[3]		0.7
Level 3
Assets:
SERP plan assets	[1]	0.0	0.0
Foreign currency exchange derivatives	[2]	0.0	0.0
Interest rate contracts	[3]		0.0
Liabilities:
Foreign currency exchange derivatives	[2]	$ 0.0	0.0
Interest rate contracts	[3]		$ 0.0

[1] Represents investments in a rabbi trust for the Company's non-qualified supplemental executive retirement plan (SERP). The fair values of these investments are determined using a market approach. Investments include mutual funds for which quoted prices in active markets are available. The Company records changes in the fair value of investments in “Miscellaneous, net” in the Condensed Consolidated Statements of Income.

[2] Based on observable market transactions of forward currency prices.

[3] Based on observable market transactions of interest rate swap prices.