Business Acquisition Business Acquisition (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Stock Repurchased During Period, Shares	2,100,000
Purchase Accounting Adjustments	$ (4,141)	$ 6,611
Business Acquisition, Purchase Price Allocation, Goodwill, Expected Tax Deductible Amount	102,400	143,300	$ 89,400
Goodwill acquired	333,190	172,593	184,837
Business Acquisition Contributed Total Revenue	52,900	52,400	51,900
Business Combination, Consideration Transferred	$ 596,074	$ 314,019	$ 300,240
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
IGC [Member]
Stock Repurchased During Period, Shares	935,231
Business Acquisition, Date of Acquisition Agreement	Jul. 12, 2016
Business Combination, Consideration Transferred	$ 6,300
Stock Repurchased During Period, Value	51,500
EVDY [Member]
Business Acquisition, Purchase Price Allocation, Goodwill, Expected Tax Deductible Amount	65,400
Goodwill acquired	263,988
Business Acquisition Contributed Total Revenue	23,200
Business Combination, Consideration Transferred	$ 493,715
Business Acquisition, Share Price	$ 10.50
Common stock, par value (in dollars per share)	$ 0.01
Business Cloud Services
Purchase Accounting Adjustments	$ 816	$ 10,900
Goodwill acquired	69,202	108,913
Digital Media
Purchase Accounting Adjustments	(4,957)	(4,289)
Goodwill acquired	$ 263,988	$ 63,680