Business Acquisitions and Divestitures (Details) - USD ($) $ in Thousands							3 Months Ended					6 Months Ended	12 Months Ended
	Oct. 30, 2015	Apr. 06, 2015	Feb. 27, 2015	Feb. 18, 2014	Nov. 08, 2013	Nov. 30, 2012	Sep. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2013	Sep. 30, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Business Acquisition [Line Items]
Acquisition related costs													$ 1,800	$ 4,200	$ 3,100
Allocation of the purchase consideration:
Goodwill								$ 1,051,294					$ 1,150,244	$ 1,051,294	$ 757,368
ADS Divesiture
Business Acquisition [Line Items]
Face value of convertible note receivable received for divestiture of a business																$ 25,000
Intangible assets acquired
Convertible note receivable converted to preferred stock amount									$ 12,500
Proceeds from conversion of note receivable												$ 12,500
Xerocole, Inc. [Member]
Business Acquisition [Line Items]
Total purchase consideration			$ 16,600
Goodwill, expected tax deductible amount			2,700
Allocation of the purchase consideration:
Goodwill			12,900
Intangible assets acquired
Gross carrying amount			$ 4,900
Weighted average useful life (in years)			8 years 9 months 18 days
Octoshape
Business Acquisition [Line Items]
Total purchase consideration		$ 107,047
Measurement period adjustment, increase (decrease) in goodwill							$ (500)
Goodwill, expected tax deductible amount		69,400
Allocation of the purchase consideration:
Cash		664
Accounts receivable		1,976
Other current assets		393
Identifiable intangible assets		41,950
Goodwill		69,445
Deferred tax assets		5,230
Total assets acquired		119,658
Other current liabilities		(1,983)
Current deferred revenue		(770)
Deferred tax liabilities		(9,858)
Total liabilities assumed		(12,611)
Net assets acquired		107,047
Intangible assets acquired
Gross carrying amount		$ 41,950
Weighted average useful life (in years)		10 years 7 months 6 days
Octoshape | Completed technologies
Intangible assets acquired
Gross carrying amount		$ 25,310
Weighted average useful life (in years)		9 years 9 months
Octoshape | Customer-related intangible assets
Intangible assets acquired
Gross carrying amount		$ 16,560
Weighted average useful life (in years)		11 years 9 months
Octoshape | Non-compete agreements
Intangible assets acquired
Gross carrying amount		$ 80
Weighted average useful life (in years)		2 years
Bloxx [Member]
Business Acquisition [Line Items]
Total purchase consideration	$ 18,700
Goodwill, expected tax deductible amount	17,700
Allocation of the purchase consideration:
Identifiable intangible assets	3,900
Goodwill	$ 17,700
Intangible assets acquired
Weighted average useful life (in years)	7 years 2 months 12 days
Prolexic
Business Acquisition [Line Items]
Total purchase consideration				$ 392,104
Measurement period adjustment, increase (decrease) in goodwill								$ 2,200
Goodwill, expected tax deductible amount				62,400
Allocation of the purchase consideration:
Cash				33,072
Accounts receivable				11,208
Property and equipment				12,225
Identifiable intangible assets				87,040
Goodwill				293,926
Deferred tax assets				16,340
Other current and long-term assets				5,664
Total assets acquired				459,475
Other current liabilities				(5,940)
Current deferred revenue				(5,812)
Deferred tax liabilities				(36,203)
Other liabilities assumed				(19,416)
Total liabilities assumed				(67,371)
Net assets acquired				392,104
Intangible assets acquired
Gross carrying amount				$ 87,040
Weighted average useful life (in years)				9 years 2 months 12 days
Prolexic | Completed technologies
Intangible assets acquired
Gross carrying amount				$ 26,800
Weighted average useful life (in years)				6 years 11 months
Prolexic | Customer-related intangible assets
Intangible assets acquired
Gross carrying amount				$ 58,500
Weighted average useful life (in years)				10 years 5 months
Prolexic | Non-compete agreements
Intangible assets acquired
Gross carrying amount				$ 940
Weighted average useful life (in years)				3 years
Prolexic | Trademarks and trade names
Intangible assets acquired
Gross carrying amount				$ 800
Weighted average useful life (in years)				4 years 11 months
Velocius
Business Acquisition [Line Items]
Total purchase consideration					$ 4,300
Contingent consideration liability					2,600
Maximum potential payout of the contingent consideration					3,000
Goodwill, expected tax deductible amount					300
Allocation of the purchase consideration:
Identifiable intangible assets					2,500
Goodwill					$ 5,400
Intangible assets acquired
Weighted average useful life (in years)					7 years 10 months 24 days
Strategic Network
Business Acquisition [Line Items]
Total purchase consideration						$ 55,000
Cost of acquired entity, cash paid										$ 27,500	$ 27,500
Allocation of the purchase consideration:
Identifiable intangible assets						16,100
Goodwill						$ 30,200
Intangible assets acquired
Weighted average useful life (in years)						9 years 9 months 18 days