BUSINESS COMBINATIONS - fair value of assets and liabilities acquired (Details) - USD ($)	12 Months Ended
	Jan. 31, 2016	Dec. 04, 2015	May. 29, 2015	Jan. 31, 2015	Jan. 31, 2014
Business Combinations
Goodwill	$ 37,405,000			$ 18,476,000	$ 18,476,000
Goodwill expected to be deductible for tax purposes	$ 12,300,000
Acquired finite-lived intangible assets weighted-average amortization period	6 years 10 months 24 days
APC
Business Combinations
Cash			$ 2,274,000
Accounts receivable			5,735,000
Costs and estimated earnings in excess of billings			3,177,000
Prepaid expenses and other assets			594,000
Property, plant and equipment			1,303,000
Intangible assets			543,000
Goodwill	$ 4,049,000		4,049,000
Less - Accounts payable and accrued expenses			5,830,000
Less - Deferred income tax and other liabilities			744,000
Net assets acquired			$ 11,101,000
Roberts
Business Combinations
Cash		$ 2,968,000
Accounts receivable		18,931,000
Costs and estimated earnings in excess of billings		2,162,000
Deferred income tax assets		4,399,000
Prepaid expenses and other assets		1,600,000
Property, plant and equipment		7,127,000
Intangible assets		7,487,000
Goodwill	$ 14,880,000	14,880,000
Less - Accounts payable and accrued expenses		34,188,000
Less - Billings in excess of costs and estimated earnings		9,229,000
Net assets acquired		$ 16,137,000