Revenue Recognition - Schedule of Increase Within Defense Segment Due to Contract Adjustments (Details) - Defense - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Disaggregation Of Revenue [Line Items]
Net sales	$ 15.6	$ 18.0	$ 24.8	$ 49.6
Operating income	10.6	11.3	14.6	41.6
Net income	$ 7.6	$ 8.7	$ 10.4	$ 31.9
Diluted earnings per share	$ 0.11	$ 0.13	$ 0.15	$ 0.45