Business Acquisitions and Divestitures (Divestitures Textual) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on sale of business	$ 13,708		$ 0
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	$ 28,800
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]
Loss on sale of business		$ (23,600)