Business Acquisitions and Divestitures (Details) (USD $)			12 Months Ended	0 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Dec. 31, 2012 Verivue, FastSoft, Blaze and Cotendo [Member]	Dec. 04, 2012 Verivue [Member]	Sep. 13, 2012 FastSoft [Member]	Mar. 06, 2012 Cotendo Acquisition [Member]	Feb. 07, 2012 Blaze Acquisition [Member]
Business Acquisition [Line Items]
Acquisition related costs			$ 5,800,000
Total purchase consideration				30,900,000	14,400,000	278,900,000	19,300,000
Business Acquisition, Contingent Consideration, at Fair Value				1,200,000
Business acquisition purchase price allocation for goodwill	729,467,000	731,325,000		20,700,000	8,900,000	233,800,000	15,100,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangibles				7,500,000	3,700,000	43,800,000	5,100,000
Weighted average amortization period (in years)				6 years 4 months 24 days	9 years	7 years 1 month 6 days	5 years 3 months 18 days
Goodwill, expected tax deductible amount				$ 5,600,000	$ 2,000,000	$ 45,000,000	$ 13,500,000