UNAUDITED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Common Stock [Member]	Additional Paid-In Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]	Total
Balance at Mar. 31, 2019	$ 143	$ 137,243	$ (53,999)	$ 341,137	$ (271)	$ 424,253
Balance (in shares) at Mar. 31, 2019	13,611
Issuance of restricted stock awards	$ 1	0	0	0	0	1
Issuance of restricted stock awards (in shares)	86
Share-based compensation	$ 0	1,919	0	0	0	1,919
Share-based compensation (in shares)	0
Repurchase of common stock	$ 0	0	$ (13,455)	0	0	(13,455)
Repurchase of common stock (in shares)			(188)
Net earnings	0	0	$ 0	16,188	0	16,188
Foreign currency translation adjustment	0	0	0	0	(263)	(263)
Balance at Jun. 30, 2019	$ 144	139,162	(67,454)	357,325	(534)	428,643
Balance (in shares) at Jun. 30, 2019	13,509
Balance at Mar. 31, 2019	$ 143	137,243	(53,999)	341,137	(271)	424,253
Balance (in shares) at Mar. 31, 2019	13,611
Net earnings						55,836
Balance at Dec. 31, 2019	$ 144	143,262	(67,691)	396,973	(202)	472,486
Balance (in shares) at Dec. 31, 2019	13,513
Balance at Jun. 30, 2019	$ 144	139,162	(67,454)	357,325	(534)	428,643
Balance (in shares) at Jun. 30, 2019	13,509
Issuance of restricted stock awards	$ 0	0	0	0	0	0
Issuance of restricted stock awards (in shares)	7
Share-based compensation	$ 0	2,135	0	0	0	2,135
Share-based compensation (in shares)	(3)
Repurchase of common stock	$ 0	0	$ (237)	0	0	(237)
Repurchase of common stock (in shares)			0
Net earnings	0	0	$ 0	20,098	0	20,098
Foreign currency translation adjustment	0	0	0	0	(350)	(350)
Balance at Sep. 30, 2019	$ 144	141,297	(67,691)	377,423	(884)	450,289
Balance (in shares) at Sep. 30, 2019	13,513
Issuance of restricted stock awards	$ 0	0	0	0	0	0
Issuance of restricted stock awards (in shares)	0
Share-based compensation	$ 0	1,965	0	0	0	1,965
Share-based compensation (in shares)	0
Repurchase of common stock	$ 0	0	$ 0	0	0	0
Repurchase of common stock (in shares)			0
Net earnings	0	0	$ 0	19,550	0	19,550
Foreign currency translation adjustment	0	0	0	0	682	682
Balance at Dec. 31, 2019	$ 144	143,262	(67,691)	396,973	(202)	472,486
Balance (in shares) at Dec. 31, 2019	13,513
Balance at Mar. 31, 2020	$ 144	145,197	(68,424)	410,219	(991)	$ 486,145
Balance (in shares) at Mar. 31, 2020	13,500					13,500
Issuance of restricted stock awards	$ 1	0	0	0	0	$ 1
Issuance of restricted stock awards (in shares)	91
Share-based compensation	$ 0	1,885	0	0	0	1,885
Share-based compensation (in shares)	0
Repurchase of common stock	$ 0	0	$ (2,703)	0	0	(2,703)
Repurchase of common stock (in shares)			(38)
Net earnings	0	0	$ 0	17,360	0	17,360
Foreign currency translation adjustment	0	0	0	0	37	37
Balance at Jun. 30, 2020	$ 145	147,082	(71,127)	427,579	(954)	502,725
Balance (in shares) at Jun. 30, 2020	13,553
Balance at Mar. 31, 2020	$ 144	145,197	(68,424)	410,219	(991)	$ 486,145
Balance (in shares) at Mar. 31, 2020	13,500					13,500
Net earnings						$ 58,844
Balance at Dec. 31, 2020	$ 145	150,624	(75,372)	469,063	549	$ 545,009
Balance (in shares) at Dec. 31, 2020	13,503					13,503
Balance at Jun. 30, 2020	$ 145	147,082	(71,127)	427,579	(954)	$ 502,725
Balance (in shares) at Jun. 30, 2020	13,553
Issuance of restricted stock awards	$ 0	0	0	0	0	0
Issuance of restricted stock awards (in shares)	8
Share-based compensation	$ 0	1,763	0	0	0	1,763
Share-based compensation (in shares)	0
Repurchase of common stock	$ 0	0	$ (1,784)	0	0	(1,784)
Repurchase of common stock (in shares)			(24)
Net earnings	0	0	$ 0	19,846	0	19,846
Foreign currency translation adjustment	0	0	0	0	520	520
Balance at Sep. 30, 2020	$ 145	148,845	(72,911)	447,425	(434)	523,070
Balance (in shares) at Sep. 30, 2020	13,537
Issuance of restricted stock awards	$ 0	0	0	0	0	0
Issuance of restricted stock awards (in shares)	1
Share-based compensation	$ 0	1,779	0	0	0	1,779
Share-based compensation (in shares)	0
Repurchase of common stock	$ 0	0	$ (2,461)	0	0	(2,461)
Repurchase of common stock (in shares)			(35)
Net earnings	0	0	$ 0	21,638	0	21,638
Foreign currency translation adjustment	0	0	0	0	983	983
Balance at Dec. 31, 2020	$ 145	$ 150,624	$ (75,372)	$ 469,063	$ 549	$ 545,009
Balance (in shares) at Dec. 31, 2020	13,503					13,503