Subsequent Event (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended		12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Mar. 31, 2020
Subsequent Event [Abstract]
Net sales		$ 461.4	$ 500.2	$ 809.2	$ 1,029.2
Goodwill		169.4		169.4		$ 166.1
Intangible assets		104.6		104.6		106.3
Automotive [Member]
Subsequent Event [Abstract]
Net sales		109.9	115.7	172.0	229.3
Automotive [Member] | Automotive and Light Vehicle [Member]
Subsequent Event [Abstract]
Net sales		97.6	$ 104.7	152.0	$ 207.1
Automotive [Member] | Liquid-Cooled Automotive Business [Member]
Subsequent Event [Abstract]
Net sales				130.0		$ 310.0
Net assets		140.0		140.0
Goodwill		0.0		0.0
Intangible assets		$ 0.0		$ 0.0
Automotive [Member] | Liquid-Cooled Automotive Business [Member] | Forecast [Member] | Minimum [Member]
Subsequent Event [Abstract]
Non-cash impairment charge	$ 120.0
Automotive [Member] | Liquid-Cooled Automotive Business [Member] | Forecast [Member] | Maximum [Member]
Subsequent Event [Abstract]
Non-cash impairment charge	$ 130.0