Goodwill And Intangible Assets (Changes In Carrying Amounts Of Goodwill And Other Intangible Assets) (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($)
Goodwill [Line Items]
Balance as of January 1, 2018	$ 1,196,611
Goodwill acquired (Note 4)	71,402
Purchase accounting adjustments (1)	(1,442)
Foreign exchange translation	5,757
Balance as of June 30, 2018	1,260,814
Business Cloud Services Segment [Member]
Goodwill [Line Items]
Balance as of January 1, 2018	603,753
Goodwill acquired (Note 4)	66,709
Purchase accounting adjustments (1)	(1,014)
Foreign exchange translation	5,339
Balance as of June 30, 2018	664,109
Digital Media Segment [Member]
Goodwill [Line Items]
Balance as of January 1, 2018	592,858
Goodwill acquired (Note 4)	4,693
Purchase accounting adjustments (1)	(428)
Foreign exchange translation	(418)
Balance as of June 30, 2018	$ 596,705