SUMMARY OF 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, 2014	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014
SUMMARY OF QUARTERLY DATA (UNAUDITED) [Abstract]
Revenues	$ 56,960	$ 52,876	$ 55,975	$ 53,090	$ 52,017	$ 56,051	$ 50,471	$ 44,054	$ 218,901	$ 202,593	$ 162,031
Gross profit	32,296	29,602	31,962	29,392	28,408	28,783	28,076	23,703	123,252	108,970	83,950
Income from continuing operations, net of tax	8,302	7,954	7,823	6,995	3,802	6,215	5,712	5,074	31,074	20,803	16,229
Gain (loss) from discontinued operations, net of tax	0	4	(7)	0	(153)	(330)	(312)	(359)	(3)	(1,154)	(2,044)
Gain on sale of discontinued operations, net of tax	559	0	0	0	7,682	0	0	0	559	7,682	0
Net income	$ 8,861	$ 7,958	$ 7,816	$ 6,995	$ 11,331	$ 5,885	$ 5,400	$ 4,715	$ 31,630	$ 27,331	$ 14,185
Basic [Abstract]
Continuing operations (in dollars per share)	$ 0.37	$ 0.35	$ 0.34	$ 0.31	$ 0.17	$ 0.27	$ 0.25	$ 0.23	$ 1.37	$ 0.92	$ 0.73
Discontinued operations (in dollars per share)	0.02	0	0	0	0.33	(0.01)	(0.01)	(0.02)	0.03	0.29	(0.09)
Basic net income per share (in dollars per share)	0.39	0.35	0.34	0.31	0.50	0.26	0.24	0.21	1.40	1.21	0.64
Diluted [Abstract]
Continuing operations (in dollars per share)	0.36	0.35	0.34	0.31	0.17	0.27	0.25	0.23	1.36	0.91	0.72
Discontinued operations (in dollars per share)	0.03	0	0	0	0.33	(0.01)	(0.01)	(0.02)	0.02	0.29	(0.09)
Diluted net income per share (in dollars per share)	0.39	0.35	0.34	0.31	0.50	0.26	0.24	0.21	1.38	1.20	0.63
Cash dividend declared (in dollars per share)	$ 0.11	$ 0.11	$ 0.11	$ 0.11	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.44	$ 0.40	$ 0