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Goodwill and Intangible Assets (Changes in Carrying Amounts of Goodwill) (Details) - USD ($) $ in Thousands			3 Months Ended		9 Months Ended
	Sep. 17, 2021	Feb. 09, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Goodwill [Roll Forward]
Balance as of January 1, 2021					$ 1,867,430
Goodwill acquired (Note 4)					85,552
Goodwill removed due to sale of businesses					(50,276)
Goodwill impairment			$ 0	$ 0	(32,629)	$ 0
Purchase accounting adjustments					(963)
Foreign exchange translation					(7,782)
Balance as of September 30, 2021			1,861,332		1,861,332
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| B2B Backup Business
Goodwill [Roll Forward]
Goodwill removed due to sale of businesses	$ (49,000)
Goodwill impairment					(32,600)
Voice, Backup, Security and CPP
Goodwill [Roll Forward]
Goodwill removed due to sale of businesses		$ (1,300)
Purchase accounting adjustments					500
Digital Media
Goodwill [Roll Forward]
Purchase accounting adjustments					(1,500)
Operating Segments \| Total Cloud Services
Goodwill [Roll Forward]
Balance as of January 1, 2021					924,496
Goodwill acquired (Note 4)					41,152
Goodwill removed due to sale of businesses					(50,276)
Goodwill impairment					(32,629)
Purchase accounting adjustments					505
Foreign exchange translation					(7,352)
Balance as of September 30, 2021			875,896		875,896
Operating Segments \| Fax and Martech
Goodwill [Roll Forward]
Balance as of January 1, 2021					425,471
Goodwill acquired (Note 4)					41,152
Goodwill removed due to sale of businesses					0
Goodwill impairment					0
Purchase accounting adjustments					0
Foreign exchange translation					(3,462)
Balance as of September 30, 2021			463,161		463,161
Operating Segments \| Voice, Backup, Security and CPP
Goodwill [Roll Forward]
Balance as of January 1, 2021					499,025
Goodwill acquired (Note 4)					0
Goodwill removed due to sale of businesses					(50,276)
Goodwill impairment					(32,629)
Purchase accounting adjustments					505
Foreign exchange translation					(3,890)
Balance as of September 30, 2021			412,735		412,735
Operating Segments \| Digital Media
Goodwill [Roll Forward]
Balance as of January 1, 2021					942,934
Goodwill acquired (Note 4)					44,400
Goodwill removed due to sale of businesses					0
Goodwill impairment					0
Purchase accounting adjustments					(1,468)
Foreign exchange translation					(430)
Balance as of September 30, 2021			$ 985,436		$ 985,436