Condensed Consolidated Statements of Income (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Income Statement [Abstract]
Revenue	$ 47,063	$ 40,468	$ 138,098	$ 123,592
Costs and expenses:
Cost of revenue	7,227	5,935	21,057	17,960
Cost of revenue-amortization of acquired technology	1,144	1,141	3,435	3,418
Total cost of revenue	8,371	7,076	24,492	21,378
Gross profit	38,692	33,392	113,606	102,214
Operating expenses:
Marketing and selling	13,361	10,632	36,466	30,943
Research and development	5,227	4,655	15,890	14,518
General and administrative	6,491	4,926	18,075	14,611
Amortization of other intangible assets	1,587	1,490	4,450	4,467
Total operating expenses	26,666	21,703	74,881	64,539
Income from operations	12,026	11,689	38,725	37,675
Other (income) expense:
Interest expense	298	271	832	1,002
Interest income	(33)	(5)	(41)	(10)
Loss on foreign exchange	817	98	987	938
(Gain) loss on derivatives	(247)	216	(33)	216
Other expense (income), net	50	8	46	(29)
Total other expense	885	588	1,791	2,117
Income before provision for income taxes	11,141	11,101	36,934	35,558
Provision for income taxes	4,102	4,037	13,759	12,567
Net income	7,039	7,064	23,175	22,991
Net income available to common shareholders-basic & diluted	$ 6,899	$ 6,950	$ 22,745	$ 22,608
Net income per common share:
Basic	$ 0.18	$ 0.18	$ 0.59	$ 0.60
Diluted	$ 0.17	$ 0.18	$ 0.57	$ 0.58
Weighted average number of shares:
Basic	38,431,031	38,276,890	38,543,401	37,717,883
Diluted	39,487,302	39,657,474	39,663,807	39,205,915
Dividends declared per common share	$ 0.08	$ 0.06	$ 0.24	$ 0.18