Acquisitions and Divestitures (Narrative) (Details) - USD ($) $ in Thousands						12 Months Ended
	Sep. 07, 2016	Feb. 29, 2016	Jan. 08, 2016	May 18, 2015	Jan. 08, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Goodwill						$ 1,966,810	$ 1,962,722	$ 1,796,851
Divestiture, earnout period		5 years
Norskale
Business Acquisition [Line Items]
Total consideration in business acquisitions	$ 11,500
Cash acquired from the acquisition	800
Goodwill	4,700
2016 Asset Acquisition
Business Acquisition [Line Items]
Finite-lived intangible assets acquired			$ 23,600
Sanbolic, Inc.
Business Acquisition [Line Items]
Total consideration in business acquisitions					$ 89,400
Cash acquired from the acquisition					200
Acquisition transaction costs					$ 500
Stock options converted and assumed (in shares)					37,057
Grasshopper Group, LLC
Business Acquisition [Line Items]
Total consideration in business acquisitions				$ 161,500
Cash acquired from the acquisition				$ 3,600
Stock options converted and assumed (in shares)				105,765
General and administrative | Norskale
Business Acquisition [Line Items]
Acquisition related costs						400
General and administrative | Sanbolic, Inc.
Business Acquisition [Line Items]
Acquisition related costs						$ 300
General and administrative | Grasshopper Group, LLC
Business Acquisition [Line Items]
Acquisition related costs							$ 300
Technology-Based Intangible Assets | Norskale
Business Acquisition [Line Items]
Finite-lived intangible assets acquired	$ 8,200
Finite-lived intangible assets acquired, Asset Life	4 years