CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
CONSOLIDATED STATEMENTS OF INCOME [Abstract]
Revenues	$ 186,025	$ 156,596	$ 143,676
Cost of revenues	87,794	71,493	63,884
Gross profit	98,231	85,103	79,792
Operating expenses:
Research and development	13,577	12,246	11,973
Sales and marketing	46,943	39,618	34,384
General and administrative	12,825	13,782	10,963
Gain from legal settlement	(17,250)	0	0
Total operating expenses	56,095	65,646	57,320
Income from operations	42,136	19,457	22,472
Interest and other income (expense), net	253	710	1,099
Income before income tax provision	42,389	20,167	23,571
Income tax provision	14,930	7,076	9,034
Net income	$ 27,459	$ 13,091	$ 14,537
Net income per share:
Basic net income per share (in dollars per share)	$ 1.25	$ 0.59	$ 0.65
Diluted net income per share (in dollars per share)	$ 1.23	$ 0.58	$ 0.64
Cash dividends declared per share (in dollars per share)	$ 1.00	$ 0	$ 0
Shares used in the calculation of net income per share:
Weighted average common shares outstanding - basic (in shares)	21,946	22,084	22,365
Weighted average common shares outstanding - diluted (in shares)	22,381	22,462	22,858