QUARTERLY DATA -UNAUDITED (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Mar. 31, 2015		Dec. 31, 2014		Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014		Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2012		Mar. 31, 2015		Mar. 31, 2014		Mar. 31, 2013
QUARTERLY DATA -UNAUDITED [Abstract]
Net sales	$ 267,265		$ 306,241		$ 297,472		$ 272,304		$ 259,908		$ 267,182		$ 271,129		$ 259,317		$ 1,143,282		$ 1,057,536		$ 983,112
Cost of sales	208,519		240,803		233,548		215,865		205,258		210,433		218,349		206,583		898,735		840,623		778,339
Gross profit	58,746		65,438		63,924		56,439		54,650		56,749		52,780		52,734		244,547		216,913		204,773
Operating expenses	43,666		44,876		43,598		41,697		40,653		38,696		38,085		39,381		173,837		156,815		146,028
Operating income	15,080		20,562		20,326		14,742		13,997		18,053		14,695		13,353		70,710		60,098		58,745
Other income	0		6,169		0		1,434										7,603		0		0
Earnings before tax	15,080		26,731		20,326		16,176										78,313		60,098		58,745
Provision for income taxes	6,170		11,230		8,374		6,699		5,775		7,443		6,104		5,503		32,473		24,825		23,915
Net earnings	$ 8,910		$ 15,501		$ 11,952		$ 9,477		$ 8,222		$ 10,610		$ 8,591		$ 7,850		$ 45,840		$ 35,273		$ 34,830
Net earnings per common share - Basic (in dollars per share)	$ 1.23	[1]	$ 2.14	[1]	$ 1.63	[1]	$ 1.26	[1]	$ 1.04	[1]	$ 1.33	[1]	$ 1.07	[1]	$ 0.98	[1]	$ 6.26	[1]	$ 4.41	[1]	$ 4.37
Net earnings per common share - Diluted (in dollars per share)	$ 1.22	[1]	$ 2.13	[1]	$ 1.63	[1]	$ 1.25	[1]	$ 1.03	[1]	$ 1.32	[1]	$ 1.06	[1]	$ 0.97	[1]	$ 6.19	[1]	$ 4.37	[1]	$ 4.32

[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.