Revenue Recognition (Details 3) $ in Thousands	Mar. 31, 2018 USD ($)
Total, Remaining Performance Obligation	$ 881,789
Amount estimated to not be recognized within 12 months	206,762
T&D [Member]
Total, Remaining Performance Obligation	359,902
Amount estimated to not be recognized within 12 months	57,413
C&I [Member]
Total, Remaining Performance Obligation	521,887
Amount estimated to not be recognized within 12 months	$ 149,349