Condensed Consolidated Statements of Income (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Income Statement [Abstract]
Revenue	$ 46,072	$ 42,039
Cost of revenue	6,508	6,009
Cost of revenue-amortization of acquired technology	1,145	1,138
Total cost of revenue	7,653	7,147
Gross profit	38,419	34,892
Operating expenses:
Marketing and selling	11,118	9,919
Research and development	5,753	4,972
General and administrative	6,198	4,705
Amortization of other intangible assets	1,432	1,490
Total operating expenses	24,501	21,086
Income from operations	13,918	13,806
Other (income) expense:
Interest expense	278	418
Interest income	(2)
Loss on foreign exchange	34	577
Loss on derivatives	56
Other	(1)	(36)
Total other expense	365	959
Income before provision for income taxes	13,553	12,847
Provision for income taxes	5,108	4,231
Net income	8,445	8,616
Net income available to common stockholders-basic	8,317	8,478
Net income available to common stockholders-diluted	$ 8,319	$ 8,481
Net income per common share:
Basic	$ 0.21	$ 0.23
Diluted	$ 0.21	$ 0.22
Weighted average number of shares:
Basic	38,712,679	37,102,507
Diluted	39,750,280	38,484,522
Dividends declared per common share	$ 0.08	$ 0.06