Consolidated Statements of Income (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Statement [Abstract]
Revenue	$ 166,624	$ 149,861	$ 123,212
Cost of revenue	23,776	21,005	10,155
Cost of revenue-amortization of acquired technology	4,560	4,051	3,169
Total cost of revenue	28,336	25,056	13,324
Gross profit	138,288	124,805	109,888
Operating expenses:
Marketing and selling	42,019	35,953	32,622
Research and development	19,897	18,007	16,540
General and administrative	19,720	18,908	17,413
Amortization of other intangible assets	5,963	5,469	5,071
Total operating expenses	87,599	78,337	71,646
Income from operations	50,689	46,468	38,242
Other (income) expense:
Interest expense	1,295	1,842	2,854
Interest income	(23)	(117)	(100)
Loss on foreign exchange	1,145	578	211
Loss on derivatives	354	11	232
Loss on extinguishment of debt			422
Other (income) expense, net	(30)	(26)	3
Total other expense	2,741	2,288	3,622
Income before provision for income taxes	47,948	44,180	34,620
Provision for income taxes	16,863	15,215	11,951
Net income	31,085	28,965	22,669
Net income available to common stockholders-basic	30,582	28,496	22,302
Net income available to common stockholders-diluted	$ 30,582	$ 28,510	$ 22,302
Net income per common share:
Basic	$ 0.81	$ 0.78	$ 0.63
Diluted	$ 0.78	$ 0.76	$ 0.61
Weighted-average number of shares outstanding-basic	37,833,817	36,311,835	35,357,630
Weighted-average number of shares outstanding-diluted	39,285,651	37,561,953	36,817,379
Dividends declared per common share	$ 0.24	$ 0.08