SEGMENT REPORTING (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2017	Oct. 31, 2016	Jan. 31, 2017
Segment Reporting Information
Revenues	$ 232,945	$ 175,444	$ 723,237	$ 468,287
Cost of revenues	195,227	138,866	594,016	359,395
GROSS PROFIT	37,718	36,578	129,221	108,892
Selling, general and administrative expenses	10,119	9,848	30,408	24,429
Impairment loss				1,979
INCOME FROM OPERATIONS	27,599	26,730	98,813	82,484
Other income, net	1,692	690	4,221	1,283
INCOME BEFORE INCOME TAXES	29,291	27,420	103,034	83,767
Income tax expense	12,062	8,194	37,738	27,122
NET INCOME	17,229	19,226	65,296	56,645
Amortization of purchased intangible assets	258	232	776	752
Depreciation	726	525	1,936	1,444
Property, plant and equipment additions	1,204	868	4,006	2,481
Current assets	583,795	499,970	583,795	499,970	$ 587,949
Current liabilities	292,316	290,533	292,316	290,533	350,724
Goodwill	34,913	34,913	34,913	34,913	34,913
Total assets	642,301	558,843	642,301	558,843	$ 644,488
Power Services
Segment Reporting Information
Revenues	212,493	151,094	662,131	402,615
Cost of revenues	178,472	118,407	540,986	302,140
GROSS PROFIT	34,021	32,687	121,145	100,475
Selling, general and administrative expenses	5,464	6,391	16,804	13,688
Impairment loss				1,979
INCOME FROM OPERATIONS	28,557	26,296	104,341	84,808
Other income, net	1,623	654	4,043	1,192
INCOME BEFORE INCOME TAXES	30,180	26,950	108,384	86,000
Amortization of purchased intangible assets	87	135	262	385
Depreciation	226	169	580	459
Property, plant and equipment additions	476	101	691	944
Current assets	488,122	410,143	488,122	410,143
Current liabilities	280,538	275,052	280,538	275,052
Goodwill	20,548	20,548	20,548	20,548
Total assets	515,783	435,208	515,783	435,208
Industrial Services
Segment Reporting Information
Revenues	16,574	21,550	50,203	59,287
Cost of revenues	13,797	18,386	44,634	52,491
GROSS PROFIT	2,777	3,164	5,569	6,796
Selling, general and administrative expenses	1,638	1,410	5,041	4,532
INCOME FROM OPERATIONS	1,139	1,754	528	2,264
INCOME BEFORE INCOME TAXES	1,139	1,754	528	2,264
Amortization of purchased intangible assets	171	97	514	367
Depreciation	425	302	1,144	841
Property, plant and equipment additions	463	481	2,800	1,082
Current assets	17,549	19,269	17,549	19,269
Current liabilities	9,546	13,336	9,546	13,336
Goodwill	14,365	14,365	14,365	14,365
Total assets	46,854	50,363	46,854	50,363
Telecom Services
Segment Reporting Information
Revenues	3,878	2,800	10,903	6,385
Cost of revenues	2,958	2,073	8,396	4,764
GROSS PROFIT	920	727	2,507	1,621
Selling, general and administrative expenses	452	316	1,163	944
INCOME FROM OPERATIONS	468	411	1,344	677
INCOME BEFORE INCOME TAXES	468	411	1,344	677
Depreciation	71	51	202	135
Property, plant and equipment additions	265	286	513	453
Current assets	4,008	2,649	4,008	2,649
Current liabilities	1,525	1,006	1,525	1,006
Total assets	5,242	3,297	5,242	3,297
Other
Segment Reporting Information
Selling, general and administrative expenses	2,565	1,731	7,400	5,265
INCOME FROM OPERATIONS	(2,565)	(1,731)	(7,400)	(5,265)
Other income, net	69	36	178	91
INCOME BEFORE INCOME TAXES	(2,496)	(1,695)	(7,222)	(5,174)
Depreciation	4	3	10	9
Property, plant and equipment additions			2	2
Current assets	74,116	67,909	74,116	67,909
Current liabilities	707	1,139	707	1,139
Total assets	74,422	$ 69,975	74,422	$ 69,975
Intercompany Eliminations
Segment Reporting Information
Revenues	$ 200		$ 1,800