Basis of Presentation - Summary of Preliminary Fair Values of Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Millions	Mar. 31, 2021	Jan. 19, 2021	Sep. 30, 2020
Assets Acquired:
Goodwill	$ 1,086.5		$ 1,009.5
Pratt Miller
Assets Acquired:
Current assets, excluding cash of $5.5		$ 15.5
Property, plant and equipment		7.8
Goodwill		75.4
Purchased intangible assets		32.3
Other long-term assets		5.8
Total assets		136.8
Liabilities Assumed:
Current liabilities		15.9
Long-term liabilities		4.8
Total liabilities		20.7
Net assets acquired		$ 116.1