Significant Accounting Policies (Reclassifications) (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017		Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues		$ 801,870	$ 732,476	$ 742,365	$ 697,192	$ 777,857	$ 690,925	$ 693,227	$ 662,677	$ 2,973,903	$ 2,824,686	[1],[2]	$ 2,736,080	[1],[2]
As Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Software as a service											175,762		134,682
Revenues											2,824,686		2,736,080
Amount Reclassified
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Software as a service											138,973		110,924
Revenues											0		0
Subscription
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues										455,276	314,735		245,606
Product and licenses
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues										734,495	766,777		810,975
Product and licenses | As Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	[3]										857,253		882,898
Product and licenses | Amount Reclassified
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	[3]										(90,476)		(71,923)
Support and services
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues										$ 1,784,132	1,743,174		1,679,499
Support and services | As Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	[4]										1,659,936		1,587,271
Support and services | Amount Reclassified
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	[4]										83,238		92,228
Professional services | As Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues											131,735		131,229
Professional services | Amount Reclassified
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues											$ (131,735)		$ (131,229)

[1] As noted above, prior period amounts have not been adjusted under the modified retrospective method of adoption of therevenue recognition standard. See Note 2 for further information regarding the Company’s adoption of the revenuerecognition standard.

[2] Prior period amounts have not been adjusted under the modified retrospective method of adoption of the revenue recognition standard. See Note 2 for further information regarding the Company’s adoption of the revenue recognition standard.

[3] Product and licenses as previously reported included revenue from CSPs and on-premise subscriptions that are now included in Subscription. Current period presentation only includes revenues from perpetual offerings and hardware.

[4] License updates and maintenance as previously reported included revenue from CSPs and on-premise license updates and maintenance that are now included in Subscription.