Condensed Consolidated Statements of Income (Unaudited) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Condensed Consolidated Statements of Income [Abstract]
Revenue	$ 42,039	$ 34,349
Cost of revenue	6,009	3,658
Cost of revenue - amortization of acquired technology	1,138	795
Total cost of revenue	7,147	4,453
Gross profit	34,892	29,896
Operating expenses:
Marketing and selling	9,919	9,271
Research and development	4,972	4,344
General and administrative	4,705	4,927
Amortization of other intangible assets	1,490	1,221
Total operating expenses	21,086	19,763
Income from operations	13,806	10,133
Other (income) expense:
Interest expense	418	451
Interest income		(7)
Loss on foreign exchange	577	267
Loss on derivatives		126
Other	(36)	(11)
Total other expense	959	826
Income before provision for income taxes	12,847	9,307
Provision for income taxes	4,231	3,587
Net income	8,616	5,720
Net income available to common stockholders - basic	8,478	5,633
Net income available to common stockholders - diluted	$ 8,481	$ 5,636
Net income per common share:
Basic	$ 0.23	$ 0.16
Diluted	$ 0.22	$ 0.15
Weighted average number of shares:
Basic	37,102,507	36,282,428
Diluted	38,484,522	37,607,047
Dividends declared per common share	$ 0.06