SEGMENT REPORTING, Reportable Segment Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) Segment	Dec. 31, 2018 USD ($)	Mar. 31, 2019 USD ($)
SEGMENT REPORTING [Abstract]
Number of business segments | Segment			2
Reportable Segment Information [Abstract]
Net sales	$ 428,991	$ 345,664	$ 1,221,928	$ 1,047,239
Cost of Sales [Abstract]
Cost of sales	325,295	262,751	922,562	798,123
Gross profit	103,696	82,913	299,366	249,116
Selling, general, and administrative	73,090	59,728	209,400	174,399
Depreciation and amortization	3,647	2,719	10,667	8,250
Interest and financing costs	694	443	1,898	1,403
Operating expenses	77,431	62,890	221,965	184,052
Operating income	26,265	20,023	77,401	65,064
Other income	997	721	912	1,140
Earnings before tax	27,262	20,744	78,313	66,204
Net Sales [Abstract]
Contracts with customers	404,918	329,635	1,163,184	1,000,776
Financing and other	5,710	5,076	13,697	15,567
Net sales	428,991	345,664	1,221,928	1,047,239
Selected Financial Data - Statement of Cash Flow [Abstract]
Depreciation and amortization	5,140	4,474	15,217	13,341
Purchases of property, equipment and operating lease equipment	2,321	2,041	7,209	8,492
Selected Financial Data - Balance Sheet [Abstract]
Total assets	952,608	798,189	952,608	798,189	$ 786,198
Product [Member]
Reportable Segment Information [Abstract]
Net sales	378,569	310,443	1,077,667	942,735
Cost of Sales [Abstract]
Cost of sales	293,209	241,856	832,135	735,802
Net Sales [Abstract]
Net sales	378,569	310,443	1,077,667	942,735
Service [Member]
Reportable Segment Information [Abstract]
Net sales	50,422	35,221	144,261	104,504
Cost of Sales [Abstract]
Cost of sales	32,086	20,895	90,427	62,321
Net Sales [Abstract]
Net sales	50,422	35,221	144,261	104,504
Technology Segment [Member]
Reportable Segment Information [Abstract]
Net sales	410,628	334,711	1,176,881	1,016,343
Net Sales [Abstract]
Contracts with customers	404,918	329,635	1,163,184	1,000,776
Financing and other	5,710	5,076	13,697	15,567
Net sales	410,628	334,711	1,176,881	1,016,343
Operating Segments [Member]
Reportable Segment Information [Abstract]
Net sales	428,991	345,664	1,221,928	1,047,239
Net Sales [Abstract]
Contracts with customers	406,607	330,448	1,167,073	1,003,245
Financing and other	22,384	15,216	54,855	43,994
Net sales	428,991	345,664	1,221,928	1,047,239
Operating Segments [Member] | Technology Segment [Member]
Reportable Segment Information [Abstract]
Net sales	410,628	334,711	1,176,881	1,016,343
Cost of Sales [Abstract]
Cost of sales	323,066	260,738	915,936	792,632
Gross profit	87,562	73,973	260,945	223,711
Selling, general, and administrative	67,759	56,607	197,615	166,199
Depreciation and amortization	3,619	2,714	10,555	8,243
Interest and financing costs	0	0	0	0
Operating expenses	71,378	59,321	208,170	174,442
Operating income	16,184	14,652	52,775	49,269
Net Sales [Abstract]
Contracts with customers	404,918	329,635	1,163,184	1,000,776
Financing and other	5,710	5,076	13,697	15,567
Net sales	410,628	334,711	1,176,881	1,016,343
Selected Financial Data - Statement of Cash Flow [Abstract]
Depreciation and amortization	3,691	2,910	10,974	8,895
Purchases of property, equipment and operating lease equipment	786	1,496	3,461	4,472
Selected Financial Data - Balance Sheet [Abstract]
Total assets	733,174	613,494	733,174	613,494
Operating Segments [Member] | Technology Segment [Member] | Product [Member]
Reportable Segment Information [Abstract]
Net sales	360,206	299,490	1,032,620	911,839
Cost of Sales [Abstract]
Cost of sales	290,980	239,843	825,509	730,311
Net Sales [Abstract]
Net sales	360,206	299,490	1,032,620	911,839
Operating Segments [Member] | Technology Segment [Member] | Service [Member]
Reportable Segment Information [Abstract]
Net sales	50,422	35,221	144,261	104,504
Cost of Sales [Abstract]
Cost of sales	32,086	20,895	90,427	62,321
Net Sales [Abstract]
Net sales	50,422	35,221	144,261	104,504
Operating Segments [Member] | Financing Segment [Member]
Reportable Segment Information [Abstract]
Net sales	18,363	10,953	45,047	30,896
Cost of Sales [Abstract]
Cost of sales	2,229	2,013	6,626	5,491
Gross profit	16,134	8,940	38,421	25,405
Selling, general, and administrative	5,331	3,121	11,785	8,200
Depreciation and amortization	28	5	112	7
Interest and financing costs	694	443	1,898	1,403
Operating expenses	6,053	3,569	13,795	9,610
Operating income	10,081	5,371	24,626	15,795
Net Sales [Abstract]
Contracts with customers	1,689	813	3,889	2,469
Financing and other	16,674	10,140	41,158	28,427
Net sales	18,363	10,953	45,047	30,896
Selected Financial Data - Statement of Cash Flow [Abstract]
Depreciation and amortization	1,449	1,564	4,243	4,446
Purchases of property, equipment and operating lease equipment	1,535	545	3,748	4,020
Selected Financial Data - Balance Sheet [Abstract]
Total assets	219,434	184,695	219,434	184,695
Operating Segments [Member] | Financing Segment [Member] | Product [Member]
Reportable Segment Information [Abstract]
Net sales	18,363	10,953	45,047	30,896
Cost of Sales [Abstract]
Cost of sales	2,229	2,013	6,626	5,491
Net Sales [Abstract]
Net sales	18,363	10,953	45,047	30,896
Operating Segments [Member] | Financing Segment [Member] | Service [Member]
Reportable Segment Information [Abstract]
Net sales	0	0	0	0
Cost of Sales [Abstract]
Cost of sales	0	0	0	0
Net Sales [Abstract]
Net sales	$ 0	$ 0	$ 0	$ 0