Goodwill And Intangible Assets (Changes In Carrying Amounts Of Goodwill And Other Intangible Assets) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
Goodwill [Line Items]
Balance as of January 1, 2018	$ 1,196,611
Goodwill acquired (Note 4)	59,068
Purchase accounting adjustments (1)	(1,004)
Foreign exchange translation	(2,846)
Balance as of March 31, 2018	1,257,521
Business Cloud Services Segment [Member]
Goodwill [Line Items]
Balance as of January 1, 2018	603,753
Goodwill acquired (Note 4)	58,033
Purchase accounting adjustments (1)	(1,014)
Foreign exchange translation	(2,993)
Balance as of March 31, 2018	663,765
Digital Media Segment [Member]
Goodwill [Line Items]
Balance as of January 1, 2018	592,858
Goodwill acquired (Note 4)	1,035
Purchase accounting adjustments (1)	(10)
Foreign exchange translation	(147)
Balance as of March 31, 2018	$ 593,756