Segment Reporting - Summarized Operating Results and Certain Financial Position Data of Company's Reportable Continuing Business Segments (Detail) (USD $)	3 Months Ended		9 Months Ended
	Oct. 31, 2014	Oct. 31, 2013	Oct. 31, 2014	Oct. 31, 2013	Jan. 31, 2014
Segment Reporting Information [Line Items]
Revenues	$ 127,564,000	$ 63,452,000	$ 280,785,000	$ 167,964,000
Cost of revenues	97,251,000	39,576,000	218,858,000	109,803,000
Gross profit	30,313,000	23,876,000	61,927,000	58,161,000
Selling, general and administrative expenses	5,473,000	3,545,000	13,332,000	8,589,000
Income (loss) from operations	24,840,000	20,331,000	48,595,000	49,572,000
Gains on the deconsolidation of VIEs				2,444,000
Other income, net	99,000	261,000	162,000	827,000
Income (loss) before income taxes	24,939,000	20,592,000	48,757,000	52,843,000
Income tax expense	8,180,000	8,143,000	15,177,000	19,531,000
Net income	16,759,000	12,449,000	33,580,000	33,312,000
Amortization of purchased intangibles	61,000	61,000	182,000	182,000
Depreciation	140,000	142,000	423,000	407,000
Property, plant and equipment additions	1,643,000	84,000	1,842,000	942,000
Goodwill	18,476,000	18,476,000	18,476,000	18,476,000	18,476,000
Total assets	414,378,000	260,448,000	414,378,000	260,448,000	323,306,000
Power Industry Services [Member]
Segment Reporting Information [Line Items]
Revenues	125,660,000	61,103,000	275,902,000	160,392,000
Cost of revenues	95,863,000	38,012,000	215,174,000	104,062,000
Telecommunications Infrastructure Services [Member]
Segment Reporting Information [Line Items]
Revenues	1,904,000	2,349,000	4,883,000	7,572,000
Cost of revenues	1,388,000	1,564,000	3,684,000	5,741,000
Operating Segments [Member] | Power Industry Services [Member]
Segment Reporting Information [Line Items]
Revenues	125,660,000	61,103,000	275,902,000	160,392,000
Cost of revenues	95,863,000	38,012,000	215,174,000	104,062,000
Gross profit	29,797,000	23,091,000	60,728,000	56,330,000
Selling, general and administrative expenses	3,486,000	1,814,000	8,042,000	5,254,000
Income (loss) from operations	26,311,000	21,277,000	52,686,000	51,076,000
Gains on the deconsolidation of VIEs				2,444,000
Other income, net	98,000	260,000	160,000	825,000
Income (loss) before income taxes	26,409,000	21,537,000	52,846,000	54,345,000
Amortization of purchased intangibles	61,000	61,000	182,000	182,000
Depreciation	94,000	96,000	286,000	268,000
Property, plant and equipment additions	1,629,000	69,000	1,718,000	880,000
Goodwill	18,476,000	18,476,000	18,476,000	18,476,000
Total assets	350,289,000	216,492,000	350,289,000	216,492,000
Operating Segments [Member] | Telecommunications Infrastructure Services [Member]
Segment Reporting Information [Line Items]
Revenues	1,904,000	2,349,000	4,883,000	7,572,000
Cost of revenues	1,388,000	1,564,000	3,684,000	5,741,000
Gross profit	516,000	785,000	1,199,000	1,831,000
Selling, general and administrative expenses	311,000	344,000	971,000	991,000
Income (loss) from operations	205,000	441,000	228,000	840,000
Income (loss) before income taxes	205,000	441,000	228,000	840,000
Depreciation	43,000	45,000	129,000	137,000
Property, plant and equipment additions	14,000	15,000	74,000	62,000
Total assets	2,833,000	2,381,000	2,833,000	2,381,000
Other [Member]
Segment Reporting Information [Line Items]
Selling, general and administrative expenses	1,676,000	1,387,000	4,319,000	2,344,000
Income (loss) from operations	(1,676,000)	(1,387,000)	(4,319,000)	(2,344,000)
Other income, net	1,000	1,000	2,000	2,000
Income (loss) before income taxes	(1,675,000)	(1,386,000)	(4,317,000)	(2,342,000)
Depreciation	3,000	1,000	8,000	2,000
Property, plant and equipment additions			50,000
Total assets	$ 61,256,000	$ 41,575,000	$ 61,256,000	$ 41,575,000