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	6,999,000	$ 0	6,999,000	$ 0	0
Stock issued under stock option plan, net of shares repurchased, shares		182,024		0
Stock-based compensation expense	3,484,000	$ 0	3,484,000	$ 0	0
Purchase of treasury stock	(22,125,000)	0	0	$ (22,125,000)	0
Purchase of treasury stock, shares				(267,120)
Net income	31,547,000	0	0	$ 0	31,547,000
Ending balance at Dec. 31, 2020	209,873,000	$ 3,000	179,675,000	$ (553,889,000)	584,084,000
Ending balance, shares at Dec. 31, 2020		54,439,754		(36,552,711)
Beginning balance at Sep. 30, 2020	202,400,000	$ 3,000	175,897,000	$ (546,204,000)	572,704,000
Beginning balance, shares at Sep. 30, 2020		54,378,892		(36,470,554)
Stock issued under stock option plan, net of shares repurchased	2,527,000	$ 0	2,527,000	$ 0	0
Stock issued under stock option plan, net of shares repurchased, shares		60,862		0
Stock-based compensation expense	1,251,000	$ 0	1,251,000	$ 0	0
Purchase of treasury stock	(7,685,000)	0	0	$ (7,685,000)	0
Purchase of treasury stock, shares				(82,157)
Net income	11,380,000	0	0	$ 0	11,380,000
Ending balance at Dec. 31, 2020	209,873,000	$ 3,000	179,675,000	$ (553,889,000)	584,084,000
Ending balance, shares at Dec. 31, 2020		54,439,754		(36,552,711)
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	8,888,000	$ 0	8,888,000	0	0
Stock issued under stock option plan, net of shares repurchased, shares		196,217
Stock-based compensation expense	3,884,000	$ 0	3,884,000	0	0
Purchase of treasury stock	$ (65,291,000)	0	0	$ (65,291,000)	0
Purchase of treasury stock, shares	(420,082)			(420,082)
Net income	$ 46,773,000	0	0	$ 0	46,773,000
Ending balance at Dec. 31, 2021	214,927,000	$ 3,000	198,984,000	$ (629,726,000)	645,666,000
Ending balance, shares at Dec. 31, 2021		54,727,393		(37,073,634)
Beginning balance at Sep. 30, 2021	223,795,000	$ 3,000	196,174,000	$ (604,190,000)	631,808,000
Beginning balance, shares at Sep. 30, 2021		54,701,476		(36,937,900)
Stock issued under stock option plan, net of shares repurchased	1,627,000	$ 0	1,627,000	$ 0	0
Stock issued under stock option plan, net of shares repurchased, shares		25,917		0
Stock-based compensation expense	1,183,000	$ 0	1,183,000	$ 0	0
Purchase of treasury stock	$ (25,536,000)	0	0	$ (25,536,000)	0
Purchase of treasury stock, shares	(135,734)			(135,734)
Net income	$ 13,858,000	0	0	$ 0	13,858,000
Ending balance at Dec. 31, 2021	$ 214,927,000	$ 3,000	$ 198,984,000	$ (629,726,000)	$ 645,666,000
Ending balance, shares at Dec. 31, 2021		54,727,393		(37,073,634)