Acquisitions - Schedule of Intangible Assets, net and Useful Life (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Sep. 30, 2019	Aug. 01, 2019	Aug. 01, 2018
APS | Capitalized software
Acquired Finite-Lived Intangible Assets [Line Items]
Identifiable intangible assets, net	$ 2.4
Useful life (in years)	3 years
Protective | APS
Acquired Finite-Lived Intangible Assets [Line Items]
Identifiable intangible assets, net	$ 80.5	$ 80.5		$ 81.1
Protective | APS | Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Identifiable intangible assets, net	$ 28.9
Useful life (in years)	13 years
Protective | APS | Trademarks and tradenames
Acquired Finite-Lived Intangible Assets [Line Items]
Identifiable intangible assets, net	$ 15.6
Useful life (in years)	9 years 1 month 6 days
Protective | APS | Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Identifiable intangible assets, net	$ 29.6
Useful life (in years)	6 years 4 months 24 days
Protective | APS | Backlog
Acquired Finite-Lived Intangible Assets [Line Items]
Identifiable intangible assets, net	$ 4.0
Useful life (in years)	4 months 24 days
Protective | AFP
Acquired Finite-Lived Intangible Assets [Line Items]
Identifiable intangible assets, net	$ 19.3		$ 19.3		$ 18.6
Protective | AFP | Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Identifiable intangible assets, net	$ 14.9
Useful life (in years)	11 years
Protective | AFP | Trademarks and tradenames
Acquired Finite-Lived Intangible Assets [Line Items]
Identifiable intangible assets, net	$ 4.4
Useful life (in years)	5 years