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, 2016	$ 131,948,000	$ 3,000	$ 130,465,000	$ (391,803,000)	$ 393,283,000
Beginning balance, shares at Mar. 31, 2016		53,448,672		(33,886,259)
Stock issued under employee stock purchase plan	419,000		419,000
Stock issued under employee stock purchase plan, shares		10,596
Stock issued under stock option plan, net of shares repurchased	2,367,000		2,367,000
Stock issued under stock option plan, net of shares repurchased, shares		109,799
Stock-based compensation expense	2,432,000		2,432,000
Purchase of treasury stock	$ (27,999,000)			$ (27,999,000)
Purchase of treasury stock, shares	(745,575)			(745,575)
Net income	$ 29,479,000				29,479,000
Ending balance at Mar. 31, 2017	138,646,000	$ 3,000	135,683,000	$ (419,802,000)	422,762,000
Ending balance, shares at Mar. 31, 2017		53,569,067		(34,631,834)
Stock issued under employee stock purchase plan	458,000		458,000
Stock issued under employee stock purchase plan, shares		8,976
Stock issued under stock option plan, net of shares repurchased	3,426,000		3,426,000
Stock issued under stock option plan, net of shares repurchased, shares		215,943
Stock-based compensation expense	3,164,000		3,164,000
Purchase of treasury stock	$ (11,187,000)			$ (11,187,000)
Purchase of treasury stock, shares	(249,245)			(249,245)
Adjustment to deferred income taxes for prior year's stock options	$ 974,000		974,000
Net income	35,695,000				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		503,000
Stock issued under employee stock purchase plan, shares	2,478,114	8,271
Stock issued under stock option plan, net of shares repurchased	$ 7,241,000		7,241,000
Stock issued under stock option plan, net of shares repurchased, shares		218,775
Stock-based compensation expense	4,349,000		4,349,000
Purchase of treasury stock	$ (35,167,000)			$ (35,167,000)
Purchase of treasury stock, shares	(582,159)			(582,159)
Net income	$ 46,703,000				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)