Consolidated Statements Of Income (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Consolidated Statements Of Income [Abstract]
Revenue	$ 42,475	$ 39,670	$ 38,505	$ 36,759	$ 36,509	$ 34,347	$ 31,851	$ 30,382	$ 157,409	$ 133,089	$ 109,862
Operating expenses:
Cost of revenue	10,128	9,036	8,492	7,923	8,047	8,368	8,685	8,095	35,579	33,195	29,640
Product development	8,170	8,005	7,219	6,657	5,563	5,266	5,016	4,377	30,051	20,222	15,711
Sales and marketing	12,795	12,713	13,017	11,089	10,738	9,907	9,379	8,860	49,614	38,884	32,835
General and administrative	8,823	7,316	9,342	6,125	6,009	5,689	5,386	3,960	31,606	21,044	17,077
Amortization of intangibles	119	11	11	77	76	11	11	11	218	109	259
Total operating expenses	40,035	37,081	38,081	31,871	30,433	29,241	28,477	25,303	147,068	113,454	95,522
Income from operations	2,440	2,589	424	4,888	6,076	5,106	3,374	5,079	10,341	19,635	14,340
Other income (expense):
Financial (expense) income	206	22	(254)	331	(132)	(780)	208	156	305	(548)	(106)
Interest income	15	19	21	16	15	18	16	14	71	63	99
Total other income (expense), net	221	41	(233)	347	(117)	(762)	224	170	376	(485)	(7)
Income before provision for income taxes	2,661	2,630	191	5,235	5,959	4,344	3,598	5,249	10,717	19,150	14,333
Provision for income taxes	1,169	1,030	51	2,112	2,083	1,609	1,402	2,018	4,362	7,112	5,074
Net income	$ 1,492	$ 1,600	$ 140	$ 3,123	$ 3,876	$ 2,735	$ 2,196	$ 3,231	$ 6,355	$ 12,038	$ 9,259
Basic net income per common share	$ 0.03	$ 0.03	$ 0.00	$ 0.06	$ 0.07	$ 0.05	$ 0.04	$ 0.06	$ 0.11	$ 0.23	$ 0.18
Diluted net income per common share	$ 0.03	$ 0.03	$ 0.00	$ 0.06	$ 0.07	$ 0.05	$ 0.04	$ 0.06	$ 0.11	$ 0.22	$ 0.18
Weighted average shares outstanding used in basic net income per common share calculation	55,892,061	55,688,824	55,146,901	54,419,498	53,563,396	53,109,824	52,735,556	52,080,363	55,292,597	52,876,999	50,721,880
Weighted average shares outstanding used in diluted net income per common share calculation	57,589,248	57,760,868	57,150,256	56,389,729	55,756,350	55,736,089	55,553,247	54,805,222	57,131,041	55,008,742	52,907,541