Acquisitions and Divestitures (Narrative) (Details) - USD ($)					3 Months Ended		9 Months Ended
	Jan. 03, 2017	Sep. 07, 2016	Feb. 29, 2016	Jan. 08, 2016	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Revenue period for earnout provision			5 years
Earnout income recognized					$ 0		$ 0
Goodwill					1,617,124,000		1,617,124,000		$ 1,585,893,000
Unidesk Corporation [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted average useful life	4 years
Preliminary consideration	$ 60,400,000
Cash acquired in business combination	2,700,000
Transaction costs	400,000
Goodwill	$ 31,231,000
Norskale [Member]
Finite-Lived Intangible Assets [Line Items]
Preliminary consideration		$ 11,500,000
Cash acquired in business combination		800,000
Transaction costs		400,000
Acquisition related costs						$ 300,000		$ 400,000
Goodwill		4,700,000
2016 Asset Acquisition [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired				$ 23,600,000
General and Administrative Expense [Member] | Unidesk Corporation [Member]
Finite-Lived Intangible Assets [Line Items]
Acquisition related costs					$ 0		$ 100,000
Core and Product Technologies [Member] | Norskale [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired		$ 8,200,000
Weighted average useful life		4 years