Quarterly Financial Information (Unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenues [Abstract]
Revenues	$ 29,039	$ 27,749	$ 26,291	$ 24,883	$ 24,657	$ 23,382	$ 22,190	$ 21,191	$ 107,962	$ 91,420	$ 76,212
Cost of revenues	6,526	6,415	5,924	5,795	4,981	4,634	4,629	4,160	24,660	18,404	13,247
Gross profit	22,513	21,334	20,367	19,088	19,676	18,748	17,561	17,031	83,302	73,016	62,965
Operating expenses:
Research and development	5,939	5,151	5,291	5,297	4,870	5,076	5,148	5,101	21,678	20,195	19,633
Sales and marketing	11,784	10,411	10,160	10,168	9,911	8,797	9,784	9,246	42,523	37,738	31,526
General and administrative	4,566	4,277	4,053	3,896	3,268	3,154	2,843	2,814	16,792	12,079	8,900
Total operating expenses	22,289	19,839	19,504	19,361	18,049	17,027	17,775	17,161	80,993	70,012	60,059
Income from operations	224	1,495	863	(273)	1,627	1,721	(214)	(130)	2,309	3,004	2,906
Other income (expense), net	(51)	24	102	(260)	(171)	23	(141)	(77)	(185)	(366)	(536)
Income before provision for income taxes	173	1,519	965	(533)	1,456	1,744	(355)	(207)	2,124	2,638	2,370
Provision for (benefit from) income taxes	128	210	92	70	281	77	(78)	78	500	358	416
Net income	45	1,309	873	(603)	1,175	1,667	(277)	(285)	1,624	2,280	1,954
Net income (loss) attributable to common stockholders	$ 45	$ 1,308	$ 872	$ (603)	$ 1,159	$ 415	$ (277)	$ (285)	$ 1,622	$ 1,076	$ 436
Earnings Per Share [Abstract]
Basic (in usd per share)	$ 0.00	$ 0.04	$ 0.03	$ (0.02)	$ 0.04	$ 0.07	$ (0.05)	$ (0.05)	$ 0.05	$ 0.09	$ 0.09
Diluted (in usd per share)	$ 0.00	$ 0.04	$ 0.02	$ (0.02)	$ 0.03	$ 0.06	$ (0.05)	$ (0.05)	$ 0.05	$ 0.08	$ 0.08