Quarterly Results of Operations (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenue:
Software license	$ 19,542	$ 16,945	$ 17,989	$ 17,107	$ 17,267	$ 14,768	$ 16,136	$ 14,245	$ 71,583	$ 62,416	$ 61,494
Services	97,073	98,518	93,519	86,913	77,786	85,025	78,203	74,887	376,023	315,901	283,872
Hardware and other	13,788	10,145	11,022	9,543	12,546	8,009	8,177	7,469	44,498	36,201	30,882
Total revenue	130,403	125,608	122,530	113,563	107,599	107,802	102,516	96,601	492,104	414,518	376,248
Costs and expenses:
Cost of license	1,970	1,679	1,848	1,613	2,564	2,445	1,937	1,778	7,110	8,724	7,838
Cost of services	45,534	43,689	41,457	38,460	36,297	35,835	35,058	35,046	169,140	142,236	128,686
Cost of hardware and other	11,088	8,496	9,265	7,479	10,142	6,812	7,023	6,214	36,328	30,191	25,213
Research and development	13,047	12,236	11,867	11,803	11,135	10,906	11,032	11,476	48,953	44,549	44,704
Sales and marketing	16,273	11,476	12,848	12,020	11,374	9,863	11,888	11,434	52,617	44,559	45,622
General and administrative	11,694	10,856	11,256	10,649	9,952	9,755	7,932	9,508	44,455	37,147	38,474
Depreciation and amortization	1,725	1,675	1,489	1,488	1,468	1,414	1,459	1,484	6,377	5,825	5,638
Total costs and expenses	101,331	90,107	90,030	83,512	82,932	77,030	76,329	76,940	364,980	313,231	296,175
Operating income	29,072	35,501	32,500	30,051	24,667	30,772	26,187	19,661	127,124	101,287	80,073
Other income (loss), net	850	(55)	312	(233)	(118)	546	1,243	151	(394)	655	(97)
Income before income taxes	29,922	35,446	32,812	29,818	24,549	31,318	27,430	19,812	127,998	103,109	81,038
Income tax provision	9,568	13,106	12,218	11,106	7,703	11,630	10,023	6,457	45,998	35,813	29,185
Net income	$ 20,354	$ 22,340	$ 20,594	$ 18,712	$ 16,846	$ 19,688	$ 17,407	$ 13,355	$ 82,000	$ 67,296	$ 51,853
Basic earnings per share	$ 0.27	$ 0.30	$ 0.27	$ 0.25	$ 0.22	$ 0.26	$ 0.23	$ 0.17	$ 1.09	$ 0.88	$ 0.66
Diluted earnings per share	$ 0.27	$ 0.30	$ 0.27	$ 0.24	$ 0.22	$ 0.25	$ 0.22	$ 0.17	$ 1.08	$ 0.86	$ 0.64
Shares used in computing basic earnings per share	74,223	74,687	75,274	75,817	76,032	76,452	76,888	77,308	74,995	76,664	78,640
Shares used in computing diluted earnings per share	75,034	75,466	76,037	76,795	77,256	77,552	78,036	78,740	75,841	77,932	81,084