Business Concentration and Credit Risks (Tables)

12 Months Ended

Dec. 31, 2017

Major customers [Member]

Concentration Risk [Line Items]

Schedule of concentration risk

Revenue (in thousands of dollars) to customers exceeding 10% of the Company’s total revenue for the years ended December 31 as indicated are as follows:

	2017			2016
	Amount		% of Total revenue	Amount		% of Total revenue
Electrical construction operations
Customer A	$	38,306	34	$	23,669	18
Customer B	—		—	18,630		14
Customer C	16,912		15	33,770		26
Customer D	11,681		10	—		—

Service/product [Member]

Concentration Risk [Line Items]

Schedule of concentration risk

Revenue by service/product (in thousands of dollars) for the years ended December 31 as indicated are as follows:

	2017			2016
	Amount		% of Total revenue	Amount		% of Total revenue
Electrical construction operations
Principal electrical construction operations (1)	$	100,305	88	$	118,748	91
Other electrical construction (2)	8,850		8	7,023		5
Total	109,154		96	125,771		96
All other	4,799		4	4,652		4
Total revenue	$	113,954	100	$	130,423	100
___________
(1) Principal electrical construction operations includes revenue from transmission lines, distribution systems, substations and drilled pier foundations. (2)Other electrical construction includes revenue from storm work, fiber optics and other miscellaneous electrical construction items.