Consolidated Statements of Stockholders' Equity - Unaudited - USD ($)	Total	Common Stock [Member]	Paid-in Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]
Beginning balance at Mar. 31, 2020	$ 189,711,000	$ 3,000	$ 168,935,000	$ (531,764,000)	$ 552,537,000
Beginning balance, shares at Mar. 31, 2020		54,254,557		(36,285,591)
Stock issued under employee stock purchase plan	257,000	$ 0	257,000	$ 0	0
Stock issued under employee stock purchase plan, shares		3,173		0
Stock issued under stock option plan, net of shares repurchased	4,472,000	$ 0	4,472,000	$ 0	0
Stock issued under stock option plan, net of shares repurchased, shares		121,162		0
Stock-based compensation expense	2,233,000	$ 0	2,233,000	$ 0	0
Purchase of treasury stock	(14,440,000)	0	0	$ (14,440,000)	0
Purchase of treasury stock, shares				(184,963)
Net income	20,167,000	0	0	$ 0	20,167,000
Ending balance at Sep. 30, 2020	202,400,000	$ 3,000	175,897,000	$ (546,204,000)	572,704,000
Ending balance, shares at Sep. 30, 2020		54,378,892		(36,470,554)
Beginning balance at Jun. 30, 2020	198,092,000	$ 3,000	171,412,000	$ (534,162,000)	560,839,000
Beginning balance, shares at Jun. 30, 2020		54,296,812		(36,320,229)
Stock issued under employee stock purchase plan	257,000	$ 0	257,000	$ 0	0
Stock issued under employee stock purchase plan, shares		3,173		0
Stock issued under stock option plan, net of shares repurchased	2,990,000	$ 0	2,990,000	$ 0	0
Stock issued under stock option plan, net of shares repurchased, shares		78,907		0
Stock-based compensation expense	1,238,000	$ 0	1,238,000	$ 0	0
Purchase of treasury stock	(12,042,000)	0	0	$ (12,042,000)	0
Purchase of treasury stock, shares				(150,325)
Net income	11,865,000	0	0	$ 0	11,865,000
Ending balance at Sep. 30, 2020	202,400,000	$ 3,000	175,897,000	$ (546,204,000)	572,704,000
Ending balance, shares at Sep. 30, 2020		54,378,892		(36,470,554)
Beginning balance at Mar. 31, 2021	220,402,000	$ 3,000	185,941,000	$ (564,435,000)	598,893,000
Beginning balance, shares at Mar. 31, 2021		54,529,642		(36,653,552)
Stock issued under employee stock purchase plan	271,000	$ 0	271,000	$ 0	0
Stock issued under employee stock purchase plan, shares		1,534
Stock issued under stock option plan, net of shares repurchased	7,261,000	$ 0	7,261,000	0	0
Stock issued under stock option plan, net of shares repurchased, shares		170,300
Stock-based compensation expense	2,701,000	$ 0	2,701,000	0	0
Purchase of treasury stock	$ (39,755,000)	0	0	$ (39,755,000)	0
Purchase of treasury stock, shares	(284,348)			(284,348)
Net income	$ 32,915,000	0	0	$ 0	32,915,000
Ending balance at Sep. 30, 2021	223,795,000	$ 3,000	196,174,000	$ (604,190,000)	631,808,000
Ending balance, shares at Sep. 30, 2021		54,701,476		(36,937,900)
Beginning balance at Jun. 30, 2021	229,539,000	$ 3,000	192,431,000	$ (578,631,000)	615,736,000
Beginning balance, shares at Jun. 30, 2021		54,642,752		(36,772,445)
Stock issued under employee stock purchase plan	271,000	$ 0	271,000	$ 0	0
Stock issued under employee stock purchase plan, shares		1,534		0
Stock issued under stock option plan, net of shares repurchased	2,117,000	$ 0	2,117,000	$ 0	0
Stock issued under stock option plan, net of shares repurchased, shares		57,190		0
Stock-based compensation expense	1,355,000	$ 0	1,355,000	$ 0	0
Purchase of treasury stock	$ (25,559,000)	0	0	$ (25,559,000)	0
Purchase of treasury stock, shares	(165,455)			(165,455)
Net income	$ 16,072,000	0	0	$ 0	16,072,000
Ending balance at Sep. 30, 2021	$ 223,795,000	$ 3,000	$ 196,174,000	$ (604,190,000)	$ 631,808,000
Ending balance, shares at Sep. 30, 2021		54,701,476		(36,937,900)