Goodwill and Intangible Assets - Additional Information (Detail) - USD ($)		3 Months Ended	12 Months Ended
	Jan. 04, 2016	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 01, 2017
Schedule Of Goodwill And Intangible Assets [Line Items]
Goodwill impairment			$ 51,200,000	$ 0	$ 0
Goodwill		$ 2,278,512,000	2,278,512,000	2,016,169,000
Impairment of indefinite-lived assets					$ 0
Foreign currency translation gain				(10,423,000)
In-process Research and Development
Schedule Of Goodwill And Intangible Assets [Line Items]
In-process R&D written off				2,200,000
Cloud Tv Reporting Unit
Schedule Of Goodwill And Intangible Assets [Line Items]
Goodwill impairment		51,200,000	51,200,000
Cloud Tv Reporting Unit | Trademarks and Trade Names
Schedule Of Goodwill And Intangible Assets [Line Items]
Impairment of indefinite-lived assets			3,800,000
Cloud Tv Reporting Unit | Non-controlling Interest
Schedule Of Goodwill And Intangible Assets [Line Items]
Goodwill impairment		17,900,000	17,900,000
Ruckus Wireless and ICX Switch business (Ruckus Networks)
Schedule Of Goodwill And Intangible Assets [Line Items]
Goodwill		318,034,000	318,034,000			$ 318,034,000
Acquired intangible assets		$ 472,500,000	$ 472,500,000			472,500,000
Ruckus Wireless and ICX Switch business (Ruckus Networks) | In-process Research and Development
Schedule Of Goodwill And Intangible Assets [Line Items]
Acquired intangible assets						$ 50,000,000
Pace Plc
Schedule Of Goodwill And Intangible Assets [Line Items]
Goodwill acquired				989,500,000
Goodwill disposed of				$ (100,000)
Acquired intangible assets	$ 1,258,700,000
Foreign currency translation gain	8,300,000
Pace Plc | Technology Licenses
Schedule Of Goodwill And Intangible Assets [Line Items]
Finite-lived intangible assets acquired	$ 5,400,000