CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2010
CONSOLIDATED STATEMENTS OF INCOME [Abstract]
Revenues	$ 156,596	$ 143,676	$ 124,557
Cost of revenues	71,493	63,884	52,435
Gross profit	85,103	79,792	72,122
Operating expenses:
Research and development	12,246	11,973	10,688
Sales and marketing	39,618	34,384	30,138
General and administrative	13,782	10,963	10,521
Total operating expenses	65,646	57,320	51,347
Income from operations	19,457	22,472	20,775
Interest and other income (expense), net	710	1,099	630
Income before income tax provision	20,167	23,571	21,405
Income tax provision	7,076	9,034	8,382
Net income	$ 13,091	$ 14,537	$ 13,023
Net income per share:
Basic net income per share (in dollars per share)	$ 0.59	$ 0.65	$ 0.59
Diluted net income per share (in dollars per share)	$ 0.58	$ 0.64	$ 0.58
Shares used in the calculation of net income per share:
Weighted average common shares outstanding - basic (in shares)	22,084	22,365	22,021
Weighted average common shares outstanding - diluted (in shares)	22,462	22,858	22,606