Employee Benefit Plans (Details Textual) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Retirement Saving Plan [Member] | Canadian employees [Member]
Defined Contribution Plans [Line Items]
Defined Contribution Plan, Cost Recognized	$ 100
Eighth District Electrical Pension Fund [Member]
Defined Contribution Plans [Line Items]
Multiemployer Plan, Collective-Bargaining Arrangement, Required Percentage of Contributions	5.00%	5.00%	5.00%
IBEW Local 1249 Pension Plan [Member]
Defined Contribution Plans [Line Items]
Multiemployer Plan, Collective-Bargaining Arrangement, Required Percentage of Contributions			5.00%
IBEW Local 769 Management Pension Plan [Member]
Defined Contribution Plans [Line Items]
Multiemployer Plan, Collective-Bargaining Arrangement, Required Percentage of Contributions			5.00%
Multiemployer Plans, Pension [Member]
Defined Contribution Plans [Line Items]
Number Of Locals Covered Under Multiemployer Defined Plans	100
Multiemployer Plans, Pension [Member] | Maximum [Member]
Defined Contribution Plans [Line Items]
Multiemployer Plans Red Zone Funded Status Percentage	65.00%
Multiemployer Plans Yellow Zone Funded Status Percentage	80.00%
Multiemployer Plans, Pension [Member] | Minimum [Member]
Defined Contribution Plans [Line Items]
Multiemployer Plans Green Zone Funded Status Percentage	80.00%
Multiemployer Plans Yellow Zone Funded Status Percentage	0.00%
Employee Benefit Plan [Member]
Defined Contribution Plans [Line Items]
Defined Contribution Plan, Cost Recognized	$ 600	$ 600	$ 700
Profit Sharing and Thrift Employee Benefit Plan [Member]
Defined Contribution Plans [Line Items]
Defined Contribution Plan, Cost Recognized	$ 3,400	$ 4,600	$ 3,400