CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
CONSOLIDATED STATEMENTS OF INCOME [Abstract]
Revenues	$ 244,700	$ 227,220	$ 218,901
Cost of revenues	111,091	101,375	95,649
Gross profit	133,609	125,845	123,252
Operating expenses:
Research and development	23,332	19,795	18,388
Sales and marketing	53,291	45,249	42,526
General and administrative	18,331	16,314	15,984
Total operating expenses	94,954	81,358	76,898
Income from operations	38,655	44,487	46,354
Interest and other income (expense), net	4,745	6,625	793
Income from continuing operations before income tax provision	43,400	51,112	47,147
Income tax provision	16,223	18,333	16,073
Income from continuing operations	27,177	32,779	31,074
Discontinued operations (Note 2)
Loss from discontinued operations, net of tax	0	(63)	(3)
Gain on sale of discontinued operations, net of tax	0	0	559
Net income	$ 27,177	$ 32,716	$ 31,630
Basic
Continuing operations (in dollars per share)	$ 1.20	$ 1.46	$ 1.37
Discontinued operations (in dollars per share)	0	(0.01)	0.03
Basic net income per share (in dollars per share)	1.20	1.45	1.40
Diluted
Continuing operations (in dollars per share)	1.17	1.44	1.36
Discontinued operations (in dollars per share)	0	0	0.02
Diluted net income per share (in dollars per share)	$ 1.17	$ 1.44	$ 1.38
Shares used in the calculation of net income per share:
Weighted average common shares outstanding - basic (in shares)	22,672,000	22,515,000	22,661,000
Weighted average common shares outstanding - diluted (in shares)	23,135,000	22,797,000	22,883,000
Cash dividends declared per share (in dollars per share)	$ 0.60	$ 0.52	$ 0.44