Consolidated Statements of Stockholders' Equity - USD ($)	Total	Common Stock [Member]	Paid-in Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]
Beginning balance at Mar. 31, 2017	$ 138,646,000	$ 3,000	$ 135,683,000	$ (419,802,000)	$ 422,762,000
Beginning balance, shares at Mar. 31, 2017		53,569,067		(34,631,834)
Stock issued under employee stock purchase plan	458,000	$ 0	458,000	$ 0	0
Stock issued under employee stock purchase plan, shares		8,976
Stock issued under stock option plan, net of shares repurchased	3,426,000	$ 0	3,426,000	0	0
Stock issued under stock option plan, net of shares repurchased, shares		215,943
Stock-based compensation expense	3,164,000	$ 0	3,164,000	0	0
Purchase of treasury stock	$ (11,187,000)	0	0	$ (11,187,000)	0
Purchase of treasury stock, shares	(249,245)			(249,245)
Adjustment to deferred income taxes for prior year's stock options	$ 974,000	0	974,000	$ 0	0
Net income	35,695,000	0	0	0	35,695,000
Ending balance at Mar. 31, 2018	171,176,000	$ 3,000	143,705,000	$ (430,989,000)	458,457,000
Ending balance, shares at Mar. 31, 2018		53,793,986		(34,881,079)
Stock issued under employee stock purchase plan	503,000	$ 0	503,000	$ 0	0
Stock issued under employee stock purchase plan, shares		8,271
Stock issued under stock option plan, net of shares repurchased	7,241,000	$ 0	7,241,000	0	0
Stock issued under stock option plan, net of shares repurchased, shares		218,775
Stock-based compensation expense	4,349,000	$ 0	4,349,000	0	0
Purchase of treasury stock	$ (35,167,000)	0	0	$ (35,167,000)	0
Purchase of treasury stock, shares	(582,159)			(582,159)
Net income	$ 46,703,000	0	0	$ 0	46,703,000
Ending balance at Mar. 31, 2019	194,805,000	$ 3,000	155,798,000	$ (466,156,000)	505,160,000
Ending balance, shares at Mar. 31, 2019		54,021,032		(35,463,238)
Stock issued under employee stock purchase plan	$ 505,000	$ 0	505,000	$ 0	0
Stock issued under employee stock purchase plan, shares	2,486,565	8,451
Stock issued under stock option plan, net of shares repurchased	$ 8,147,000	$ 0	8,147,000	0	0
Stock issued under stock option plan, net of shares repurchased, shares		225,074
Stock-based compensation expense	4,485,000	$ 0	4,485,000	0	0
Purchase of treasury stock	$ (65,608,000)	0	0	$ (65,608,000)	0
Purchase of treasury stock, shares	(822,353)			(822,353)
Net income	$ 47,377,000	0	0	$ 0	47,377,000
Ending balance at Mar. 31, 2020	$ 189,711,000	$ 3,000	$ 168,935,000	$ (531,764,000)	$ 552,537,000
Ending balance, shares at Mar. 31, 2020		54,254,557		(36,285,591)