Goodwill and Other Intangible Assets - Summary of Activity in Goodwill (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014
Goodwill [Line Items]
Beginning balance	$ 1,884,920	$ 1,671,205
Acquisitions	47,800	234,964
Foreign currency translation adjustment	(16,677)	(21,023)
Acquisition accounting adjustments	(353)	(226)
Ending balance	1,915,690	1,884,920
Unified Communications Services [Member]
Goodwill [Line Items]
Beginning balance	864,568	885,416
Acquisitions	24,579
Foreign currency translation adjustment	(15,365)	(20,848)
Ending balance	873,782	864,568
Safety Services [Member]
Goodwill [Line Items]
Beginning balance	507,588	487,390
Acquisitions		20,198
Acquisition accounting adjustments	1,091
Ending balance	508,679	507,588
Interactive Services [Member]
Goodwill [Line Items]
Beginning balance	223,014	166,063
Acquisitions	23,221	57,352
Foreign currency translation adjustment	(1,312)	(175)
Acquisition accounting adjustments	(44)	(226)
Ending balance	244,879	223,014
Specialized Agent Services [Member]
Goodwill [Line Items]
Beginning balance	289,750	132,336
Acquisitions		157,414
Acquisition accounting adjustments	(1,400)
Ending balance	$ 288,350	$ 289,750

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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