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Employee Benefit Plans (Details Textual) $ in Thousands | 12 Months Ended
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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

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- Definition Amount of cost for defined contribution plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942 + Details
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- Definition Percentage of contributions required by collective bargaining arrangement to all contributions required of employer for pension and other postretirement plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 80 -Section 50 -Paragraph 5 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450657-114947 + Details
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