Revenue Recognition (Details 1) $ in Thousands	3 Months Ended
Mar. 31, 2018 USD ($)
Revenues	$ 345,611
Concentration Risk, Percentage	100.00%
T&D [Member]
Revenues	$ 216,386
Concentration Risk, Percentage	100.00%
T&D [Member] \| Market Type Transmission [Member]
Revenues	$ 134,452
Concentration Risk, Percentage	38.90%
T&D [Member] \| Market Type Distribution [Member]
Revenues	$ 81,934
Concentration Risk, Percentage	23.70%
C&I [Member]
Revenues	$ 129,225
Concentration Risk, Percentage	100.00%
C&I [Member] \| Market Type Electrical Construction [Member]
Revenues	$ 129,225
Concentration Risk, Percentage	37.40%

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=84177426&loc=d3e6351-108592

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13531-108611

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=84177426&loc=d3e6404-108592

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13537-108611

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Data Type:	num:percentItemType
Balance Type:	na
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