QUARTERLY DATA -UNAUDITED (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Mar. 31, 2016		Dec. 31, 2015		Sep. 30, 2015		Jun. 30, 2015		Mar. 31, 2015		Dec. 31, 2014		Sep. 30, 2014		Jun. 30, 2013		Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014
QUARTERLY DATA -UNAUDITED [Abstract]
Net sales	$ 299,403		$ 298,644		$ 336,286		$ 269,866		$ 267,265		$ 306,241		$ 297,472		$ 272,304		$ 1,204,199	$ 1,143,282	$ 1,057,536
Cost of sales	232,457		234,584		264,365		210,736		208,519		240,803		233,548		215,865		942,142	898,735	840,623
Gross profit	66,946		64,060		71,921		59,130		58,746		65,438		63,924		56,439		262,057	244,547	216,913
Operating expenses	50,567		46,415		45,260		44,064		43,666		44,876		43,598		41,697		186,306	173,837	156,815
Operating income	16,379		17,645		26,661		15,066		15,080		20,562		20,326		14,742		75,751	70,710	60,098
Other income									0		6,169		0		1,434		0	7,603	0
Earnings before tax	16,379		17,645		26,661		15,066		15,080		26,731		20,326		16,176		75,751	78,313	60,098
Provision for income taxes	6,422		7,348		10,982		6,252		6,170		11,230		8,374		6,699		31,004	32,473	24,825
Net earnings	$ 9,957		$ 10,297		$ 15,679		$ 8,814		$ 8,910		$ 15,501		$ 11,952		$ 9,477		$ 44,747	$ 45,840	$ 35,273
Net earnings per common share - Basic (in dollars per share)	$ 1.37	[1]	$ 1.41	[1]	$ 2.16	[1]	$ 1.22	[1]	$ 1.23	[1]	$ 2.14	[1]	$ 1.63	[1]	$ 1.26	[1]	$ 6.17	$ 6.26	$ 4.41
Net earnings per common share - Diluted (in dollars per share)	$ 1.36	[1]	$ 1.40	[1]	$ 2.15	[1]	$ 1.21	[1]	$ 1.22	[1]	$ 2.13	[1]	$ 1.63	[1]	$ 1.25	[1]	$ 6.09	$ 6.19	$ 4.37

[1] Basic and diluted earnings per share are computed independently for each of the quarters presented. Therefore, the sum of quarterly basic and diluted per share information may not equal annual basic and diluted earnings per share.