Business Acquisitions and Divestitures Divestitures Textual (Detail) - USD ($) $ in Millions			12 Months Ended		24 Months Ended
	May 01, 2019	Oct. 16, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Feb. 06, 2018
Held-for-sale [Member] | Consumer and Small and Medium-Sized Security Business [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Carrying amount of disposal group						$ 28.8
Pre-tax loss on net asset held for sale			$ 13.7	$ 23.6	$ 37.3
SeaPilot [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Business Combination, Consideration Transferred		$ 4.6
NEOS [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Business Combination, Consideration Transferred	$ 22.2