Goodwill and Intangible Assets (Changes in Carrying Amounts of Goodwill) (Details) - USD ($) $ in Thousands		3 Months Ended
	Feb. 09, 2021	Mar. 31, 2021
Goodwill [Line Items]
Balance as of January 1, 2021		$ 1,867,430
Goodwill written off related to sale of a business		(1,339)
Goodwill reclassified to noncurrent assets held for sale		(86,389)
Purchase accounting adjustments		2,790
Foreign exchange translation		(4,747)
Balance as of March 31, 2021		1,777,745
Voice, Backup, Security and CPP
Goodwill [Line Items]
Goodwill written off related to sale of a business	$ (1,300)
Operating Segments | Total Cloud Services
Goodwill [Line Items]
Balance as of January 1, 2021		924,496
Goodwill written off related to sale of a business		(1,339)
Goodwill reclassified to noncurrent assets held for sale		(86,389)
Purchase accounting adjustments		254
Foreign exchange translation		(4,558)
Balance as of March 31, 2021		832,464
Operating Segments | Fax and Martech
Goodwill [Line Items]
Balance as of January 1, 2021		425,471
Goodwill written off related to sale of a business		0
Goodwill reclassified to noncurrent assets held for sale		0
Purchase accounting adjustments		0
Foreign exchange translation		(2,923)
Balance as of March 31, 2021		422,548
Operating Segments | Voice, Backup, Security and CPP
Goodwill [Line Items]
Balance as of January 1, 2021		499,025
Goodwill written off related to sale of a business		(1,339)
Goodwill reclassified to noncurrent assets held for sale		(86,389)
Purchase accounting adjustments		254
Foreign exchange translation		(1,635)
Balance as of March 31, 2021		409,916
Operating Segments | Digital Media
Goodwill [Line Items]
Balance as of January 1, 2021		942,934
Goodwill written off related to sale of a business		0
Goodwill reclassified to noncurrent assets held for sale		0
Purchase accounting adjustments		2,536
Foreign exchange translation		(189)
Balance as of March 31, 2021		$ 945,281