Recent Accounting Standards - Line Items Adjusted in Consolidated Statement of Operations (Detail) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Revenues		$ 120,602	$ 119,220	$ 243,569	$ 241,452
Sales and marketing expenses		50,978	41,626	102,313	81,208
Provision for income taxes		1,059	2,668	541	6,927
Net income		$ 4,828	$ 9,953	$ 6,501	$ 25,510
Diluted earnings per share	[1]	$ 0.42	$ 0.86	$ 0.57	$ 2.20
Product licenses
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Revenues		$ 19,292	$ 17,728	$ 36,593	$ 40,374
Product support
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Revenues		$ 73,676	70,766	$ 148,091	141,278
As Reported
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Sales and marketing expenses			41,419		80,829
Provision for income taxes			3,142		6,607
Net income			$ 11,076		$ 25,943
Diluted earnings per share			$ 0.96		$ 2.24
As Reported | Product licenses
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Revenues			$ 19,118		$ 40,130
As Reported | Product support
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Revenues					141,256
Effect of the Adoption | ASU 2014-09
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Sales and marketing expenses			207		379
Provision for income taxes			(474)		320
Net income			$ (1,123)		$ (433)
Diluted earnings per share			$ (0.10)		$ (0.04)
Effect of the Adoption | Product licenses | ASU 2014-09
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Revenues			$ (1,390)		$ 244
Effect of the Adoption | Product support | ASU 2014-09
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Revenues					$ 22

[1] Basic and fully diluted earnings per share for class A and class B common stock are the same.