SEGMENT REPORTING (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Jan. 31, 2017 USD ($)	Oct. 31, 2016 USD ($)	Jul. 31, 2016 USD ($)	Apr. 30, 2016 USD ($)	Jan. 31, 2016 USD ($)	Oct. 31, 2015 USD ($)	Jul. 31, 2015 USD ($)	Apr. 30, 2015 USD ($)	Jan. 31, 2017 USD ($) item	Jan. 31, 2016 USD ($)	Jan. 31, 2015 USD ($)
Segment Reporting Information
Operating segment | item									1
Revenues	$ 206,760	$ 175,444	$ 162,495	$ 130,348	$ 116,386	$ 113,967	$ 97,434	$ 85,488	$ 675,047	$ 413,275	$ 383,110
Cost of revenues									528,336	313,810	299,507
Gross profit	37,819	36,578	44,012	28,302	23,543	26,262	28,493	21,167	146,711	99,465	83,603
Selling, general and administrative expenses									32,478	25,060	19,470
Impairment loss									1,979
Income (loss) from operations	29,770	26,730	34,499	21,255	14,461	20,672	23,645	15,627	112,254	74,405	64,133
Other income, net									2,278	1,101	234
Income (loss) before income taxes									114,532	75,506	64,367
Income tax expense									37,106	25,302	20,912
Net income	20,781	$ 19,226	$ 23,299	$ 14,120	9,160	$ 14,359	$ 15,834	$ 10,851	77,426	50,204	43,455
Amortization expense									1,163	531	243
Depreciation									2,043	779	551
Property, plant and equipment additions									2,811	3,118	2,936
Current assets	587,949				350,612				587,949	350,612
Current liabilities	350,724				187,712				350,724	187,712
Goodwill	34,913				37,405				34,913	37,405	18,476
Total assets	644,247				409,791				644,247	409,791	391,193
Power industry services
Segment Reporting Information
Revenues									586,628	387,636	376,676
Cost of revenues									452,599	290,823	294,643
Gross profit									134,029	96,813	82,033
Selling, general and administrative expenses									17,588	15,303	11,930
Impairment loss									1,979
Income (loss) from operations									114,462	81,510	70,103
Other income, net									2,145	827	231
Income (loss) before income taxes									116,607	82,337	70,334
Amortization expense									350	415	243
Depreciation									665	433	372
Property, plant and equipment additions									1,005	2,985	2,807
Current assets	461,086								461,086
Current liabilities	337,617								337,617
Goodwill	20,548				22,525				20,548	22,525	18,476
Total assets	488,431				274,627				488,431	274,627	303,737
Telecommunications infrastructure services
Segment Reporting Information
Revenues									9,425	10,379	6,434
Cost of revenues									7,383	7,460	4,864
Gross profit									2,042	2,919	1,570
Selling, general and administrative expenses									1,430	1,323	1,299
Income (loss) from operations									612	1,596	271
Income (loss) before income taxes									612	1,596	271
Depreciation									201	162	169
Property, plant and equipment additions									563	100	77
Current assets	3,399								3,399
Current liabilities	1,012								1,012
Total assets	4,318				1,885				4,318	1,885	2,293
Industrial fabrication and field services
Segment Reporting Information
Revenues									78,994	15,260
Cost of revenues									68,354	15,527
Gross profit									10,640	(267)
Selling, general and administrative expenses									6,264	1,151
Income (loss) from operations									4,376	(1,418)
Income (loss) before income taxes									4,376	(1,418)
Amortization expense									813	116
Depreciation									1,165	172
Property, plant and equipment additions									1,238	28
Current assets	19,329								19,329
Current liabilities	10,335								10,335
Goodwill	14,365				14,880				14,365	14,880
Total assets	47,316				52,436				47,316	52,436
Other
Segment Reporting Information
Selling, general and administrative expenses									7,196	7,283	6,241
Income (loss) from operations									(7,196)	(7,283)	(6,241)
Other income, net									133	274	3
Income (loss) before income taxes									(7,063)	(7,009)	(6,238)
Depreciation									12	12	10
Property, plant and equipment additions									5	5	52
Current assets	104,135								104,135
Current liabilities	1,760								1,760
Total assets	$ 104,182				$ 80,843				$ 104,182	$ 80,843	$ 85,163