Revenue Recognition - Schedule of revenue by market type (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Amount	$ 518,470	$ 468,094
Revenue from Contract with Customer [Member]
Disaggregation of Revenue [Line Items]
Amount	$ 518,470	$ 468,094
Concentration risk	100.00%	100.00%
T&D [Member] | Revenue from Contract with Customer [Member]
Disaggregation of Revenue [Line Items]
Amount	$ 259,270	$ 272,548
Concentration risk	100.00%	100.00%
T&D [Member] | Market Type Transmission [Member] | Revenue from Contract with Customer [Member]
Disaggregation of Revenue [Line Items]
Amount	$ 171,566	$ 187,765
Concentration risk	33.10%	40.10%
T&D [Member] | Market Type Distribution [Member] | Revenue from Contract with Customer [Member]
Disaggregation of Revenue [Line Items]
Amount	$ 87,704	$ 84,783
Concentration risk	16.90%	18.10%
C&I [Member] | Revenue from Contract with Customer [Member]
Disaggregation of Revenue [Line Items]
Amount	$ 259,200	$ 195,546
Concentration risk	100.00%	100.00%
C&I [Member] | Market Type Electrical construction [Member] | Revenue from Contract with Customer [Member]
Disaggregation of Revenue [Line Items]
Amount	$ 259,200	$ 195,546
Concentration risk	50.00%	41.80%