Business Concentration and Credit Risks (Details) - USD ($)	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Concentration Risk [Line Items]
Accounts receivable and accrued billings, net	$ 21,566,842	$ 19,094,407
Revenues	113,953,519	130,423,463
Revenue [Member] \| Major customers [Member] \| Customer A [Member]
Concentration Risk [Line Items]
Revenues	$ 38,306,000	$ 23,669,000
Concentration risk, percentage	34.00%	18.00%
Revenue [Member] \| Major customers [Member] \| Customer B [Member]
Concentration Risk [Line Items]
Revenues	$ 0	$ 18,630,000
Concentration risk, percentage	0.00%	14.00%
Revenue [Member] \| Major customers [Member] \| Customer C [Member]
Concentration Risk [Line Items]
Revenues	$ 16,912,000	$ 33,770,000
Concentration risk, percentage	15.00%	26.00%
Revenue [Member] \| Major customers [Member] \| Customer D [Member]
Concentration Risk [Line Items]
Revenues	$ 11,681,000	$ 0
Concentration risk, percentage	10.00%	0.00%
Revenue [Member] \| Service/product [Member]
Concentration Risk [Line Items]
Revenues	$ 113,954,000	$ 130,423,000
Concentration risk, percentage	100.00%	100.00%
Revenue [Member] \| Service/product [Member] \| Electrical Construction [Member]
Concentration Risk [Line Items]
Revenues	$ 109,154,000	$ 125,771,000
Concentration risk, percentage	96.00%	96.00%
Revenue [Member] \| Service/product [Member] \| Principal electrical construction operations [Member]
Concentration Risk [Line Items]
Revenues	$ 100,305,000	$ 118,748,000
Concentration risk, percentage	88.00%	91.00%
Revenue [Member] \| Service/product [Member] \| Other electrical construction [Member]
Concentration Risk [Line Items]
Revenues	$ 8,850,000	$ 7,023,000
Concentration risk, percentage	8.00%	5.00%
Revenue [Member] \| Service/product [Member] \| All other [Member]
Concentration Risk [Line Items]
Revenues	$ 4,799,000	$ 4,652,000
Concentration risk, percentage	4.00%	4.00%

Amount due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer), for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(3))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(4))
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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
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