Quarterly Results of Operations (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue:
Total revenue	$ 147,082	$ 149,757	$ 135,630	$ 153,903	$ 152,929	$ 162,275	$ 154,341	$ 148,404	$ 586,372	$ 617,949	$ 559,157
Costs and expenses:
Total costs									269,887	284,967	240,881
Research and development	20,563	20,454	19,931	23,328	21,784	22,614	21,997	21,213	84,276	87,608	71,896
Sales and marketing	13,562	11,399	9,709	13,088	15,434	12,125	14,520	14,781	47,758	56,860	51,262
General and administrative	15,778	15,536	14,016	16,114	16,512	16,236	16,805	15,050	61,444	64,603	52,618
Depreciation and amortization	2,150	2,193	2,257	2,346	2,277	1,937	1,859	1,914	8,946	7,987	8,613
Total costs and expenses	118,885	114,781	108,938	129,707	127,860	127,278	126,759	120,128	472,311	502,025	425,270
Operating income	28,197	34,976	26,692	24,196	25,069	34,997	27,582	28,276	114,061	115,924	133,887
Other (loss) income, net	(656)	(891)	(158)	1,420	(215)	810	(71)	(371)
Income before income taxes	27,541	34,085	26,534	25,616	24,854	35,807	27,511	27,905	113,776	116,077	136,231
Income tax provision	7,001	9,119	7,330	3,086	8,096	8,700	6,586	6,933	26,536	30,315	31,541
Net income	$ 20,540	$ 24,966	$ 19,204	$ 22,530	$ 16,758	$ 27,107	$ 20,925	$ 20,972	$ 87,240	$ 85,762	$ 104,690
Basic earnings per share	$ 0.32	$ 0.39	$ 0.30	$ 0.35	$ 0.26	$ 0.42	$ 0.32	$ 0.32	$ 1.37	$ 1.33	$ 1.58
Diluted earnings per share	$ 0.32	$ 0.39	$ 0.30	$ 0.35	$ 0.26	$ 0.42	$ 0.32	$ 0.32	$ 1.36	$ 1.32	$ 1.58
Shares used in computing basic earnings per share	63,527	63,524	63,509	63,592	63,822	64,247	64,623	64,909	63,538	64,397	66,201
Shares used in computing diluted earnings per share	64,484	64,427	64,126	64,342	64,807	64,992	65,093	65,204	64,333	65,103	66,434
Cloud Subscriptions
Revenue:
Total revenue	$ 23,003	$ 21,064	$ 18,503	$ 17,260	$ 15,721	$ 14,242	$ 9,009	$ 7,859	$ 79,830	$ 46,831	$ 23,104
Software License
Revenue:
Total revenue	9,635	13,233	5,681	9,735	9,234	15,486	11,721	12,414	38,284	48,855	45,368
Costs and expenses:
Total costs	1,221	527	591	555	663	748	623	592	2,894	2,626	5,297
Maintenance
Revenue:
Total revenue	38,801	37,305	35,898	35,744	38,045	37,763	37,323	36,099	147,748	149,230	147,033
Services
Revenue:
Total revenue	70,915	73,470	71,778	87,406	86,308	91,626	93,951	88,631	303,569	360,516	329,685
Hardware
Revenue:
Total revenue	4,728	4,685	3,770	3,758	3,621	3,158	2,337	3,401	16,941	12,517	13,967
Cloud Subscriptions, Maintenance and Services
Costs and expenses:
Total costs	$ 65,611	$ 64,672	$ 62,434	$ 74,276	$ 71,190	$ 73,618	$ 70,955	$ 66,578	$ 266,993	$ 282,341	$ 235,584