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, 2018	$ 142	$ 130,000	$ (36,016)	$ 277,945	$ 532	$ 372,603
Balance (in shares) at Mar. 31, 2018	13,761
Issuance of restricted stock awards	$ 1	0	0	0	0	1
Issuance of restricted stock awards (in shares)	70
Share-based compensation	$ 0	1,693	0	0	0	1,693
Repurchase of common stock	0	0	$ (9,059)	0	0	(9,059)
Repurchase of common stock (in shares)			(108)
Net earnings	0	0	$ 0	15,273	0	15,273
Foreign currency translation adjustment	0	0	0	0	(657)	(657)
Balance at Jun. 30, 2018	$ 143	131,693	(45,075)	293,218	(125)	379,854
Balance (in shares) at Jun. 30, 2018	13,723
Balance at Mar. 31, 2018	$ 142	130,000	(36,016)	277,945	532	372,603
Balance (in shares) at Mar. 31, 2018	13,761
Net earnings						48,140
Balance at Dec. 31, 2018	$ 143	135,418	(51,899)	326,085	(570)	409,177
Balance (in shares) at Dec. 31, 2018	13,640
Balance at Jun. 30, 2018	$ 143	131,693	(45,075)	293,218	(125)	379,854
Balance (in shares) at Jun. 30, 2018	13,723
Issuance of restricted stock awards	$ 0	0	0	0	0	0
Issuance of restricted stock awards (in shares)	7
Share-based compensation	$ 0	1,868	0	0	0	1,868
Repurchase of common stock	0	0	$ (305)	0	0	(305)
Repurchase of common stock (in shares)			(3)
Net earnings	0	0	$ 0	18,003	0	18,003
Foreign currency translation adjustment	0	0	0	0	(143)	(143)
Balance at Sep. 30, 2018	$ 143	133,561	(45,380)	311,221	(268)	399,277
Balance (in shares) at Sep. 30, 2018	13,727
Issuance of restricted stock awards	$ 0	0	0	0	0	0
Issuance of restricted stock awards (in shares)	(2)
Share-based compensation	$ 0	1,857	0	0	0	1,857
Repurchase of common stock	0	0	$ (6,519)	0	0	(6,519)
Repurchase of common stock (in shares)			(85)
Net earnings	0	0	$ 0	14,864	0	14,864
Foreign currency translation adjustment	0	0	0	0	(302)	(302)
Balance at Dec. 31, 2018	$ 143	135,418	(51,899)	326,085	(570)	409,177
Balance (in shares) at Dec. 31, 2018	13,640
Balance at Mar. 31, 2019	$ 143	137,243	(53,999)	341,137	(271)	$ 424,253
Balance (in shares) at Mar. 31, 2019	13,611					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
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					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					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)	0
Repurchase of common stock	$ 0	0	$ (237)	0	0	(237)
Repurchase of common stock (in shares)			(3)
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					13,513