Business Acquisitions - Narrative (Details) (USD $)			0 Months Ended	9 Months Ended	0 Months Ended		0 Months Ended	3 Months Ended
	Sep. 30, 2014	Dec. 31, 2013	Feb. 18, 2014 Prolexic Technologies, Inc.	Sep. 30, 2014 Prolexic Technologies, Inc.	Nov. 08, 2013 Velocius	Sep. 30, 2014 Velocius	Nov. 30, 2012 Strategic Network Acquisition	Mar. 31, 2014 Strategic Network Acquisition	Sep. 30, 2013 Strategic Network Acquisition
Business Acquisition [Line Items]
Total purchase consideration			$ 392,104,000		$ 4,300,000		$ 55,000,000.0
Acquisition-related costs				4,100,000
Contingent consideration liability					2,600,000	900,000
Maximum potential payout of the contingent consideration					3,000,000
Allocated to goodwill	1,049,047,000	757,368,000	291,679,000		5,400,000
Allocated to intangible assets			87,040,000		2,500,000
Weighted Average Useful Life (in years)					7 years 10 months 24 days
Goodwill, expected tax deductible amount			62,400,000		300,000
Consideration paid								$ 27,500,000	$ 27,500,000