Goodwill And Intangible Assets (Changes In Carrying Amounts Of Goodwill And Other Intangible Assets) (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2020 USD ($)
Goodwill [Line Items]
Balance as of January 1, 2020	$ 1,633,033
Goodwill acquired (Note 4)	16,466
Goodwill, Transfers	(13,595)
Purchase accounting adjustments (2)	6,935
Foreign exchange translation	(5,552)
Balance as of June 30, 2020	1,637,287
Disposal Group, Held-for-sale, Not Discontinued Operations
Goodwill [Line Items]
Disposal Group, Including Discontinued Operation, Goodwill	13,595
Fax and Martech [Member]
Goodwill [Line Items]
Balance as of January 1, 2020	397,788
Goodwill acquired (Note 4)	15,844
Goodwill, Transfers	0
Purchase accounting adjustments (2)	0
Foreign exchange translation	(685)
Balance as of June 30, 2020	412,947
Voice, Backup, Security and CPP [Member]
Goodwill [Line Items]
Balance as of January 1, 2020	480,084
Goodwill acquired (Note 4)	0
Goodwill, Transfers	(13,595)
Purchase accounting adjustments (2)	2,130
Foreign exchange translation	(4,325)
Balance as of June 30, 2020	460,034
Cloud Services Segment [Member]
Goodwill [Line Items]
Balance as of January 1, 2020	877,872
Goodwill acquired (Note 4)	15,844
Goodwill, Transfers	(13,595)
Purchase accounting adjustments (2)	2,130
Foreign exchange translation	(5,010)
Balance as of June 30, 2020	872,981
Digital Media Segment [Member]
Goodwill [Line Items]
Balance as of January 1, 2020	755,161
Goodwill acquired (Note 4)	622
Goodwill, Transfers	0
Purchase accounting adjustments (2)	9,065
Foreign exchange translation	(542)
Balance as of June 30, 2020	$ 764,306