Sale of Equity Affiliate (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Schedule of Equity Method Investments [Line Items]
Income tax provision		$ 30.1	$ 19.6	$ 14.2	$ 55.0	$ 11.9	$ 14.4	$ 11.5	$ 15.2	$ 118.9	$ 53.0	$ 58.8
Daido Air Products Electronics, Inc. | Disposed of by Sale
Schedule of Equity Method Investments [Line Items]
Proceeds from sale of equity method investment	$ 15.9
Realized gain on sale of equity method investment												0.7
Investment in net assets of and advances to equity affiliates	12.8
Foreign currency translation loss	$ 2.4
Income tax provision												$ 5.3