Unaudited Quarterly Information (Details) (USD $) In Thousands, except Per 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
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 37,028	$ 35,447	$ 39,360	$ 39,333	$ 35,156	$ 38,661	$ 37,565	$ 36,960	$ 151,168	$ 148,342	$ 112,784
Cost of revenues	4,072	3,989	3,630	4,054	3,680	4,221	2,940	2,442	15,745	13,283	7,253
Gross profit	32,956	31,458	35,730	35,279	31,476	34,440	34,625	34,518	135,423	135,059	105,531
Operating expenses:
Sales and marketing	18,489	17,427	16,061	16,265	13,921	16,737	18,701	16,131	68,242	65,490	54,454
General and administrative	10,109	9,836	9,303	9,444	9,380	8,478	8,295	8,394	38,692	34,547	27,565
Unexchanged promotional merger share	0	0	0	3,000	0	0	0	20,000	3,000	20,000	0
Total operating expenses	28,598	27,263	25,364	28,709	23,301	25,215	26,996	44,525	109,934	120,037	82,019
Operating income(loss)	4,358	4,195	10,366	6,570	8,175	9,225	7,629	(10,007)	25,489	15,022	23,512
Interest income and other income	92	89	59	64	255	52	43	32	305	383	166
Gain (loss) on foreign currency	(1)	46	(75)	35	(58)	(52)	(1)	31	4	(81)	(197)
Income before income taxes	4,449	4,330	10,350	6,669	8,372	9,225	7,671	(9,944)	25,798	15,324	23,481
Income tax expense	692	896	3,090	2,922	1,944	3,298	2,752	4,011	7,600	12,005	10,324
Net income	$ 3,757	$ 3,434	$ 7,260	$ 3,747	$ 6,428	$ 5,927	$ 4,919	$ (13,955)	$ 18,198	$ 3,319	$ 13,157
Basic net income (loss) per share (in dollars per share)	$ 0.24	$ 0.22	$ 0.45	$ 0.23	$ 0.40	$ 0.36	$ 0.30	$ (0.85)	$ 1.15	$ 0.20	$ 0.80
Diluted Net income (loss) per share (in dollars per share)	$ 0.25	$ 0.22	$ 0.45	$ 0.23	$ 0.40	$ 0.36	$ 0.30	$ (0.85)	$ 1.14	$ 0.20	$ 0.80