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Labor Union Contracts (Details) - Workforce subject to collective bargaining arrangements, effective June 18, 2017
6 Months Ended
Jun. 30, 2017
Concentration Risk [Line Items]  
Collective bargaining arrangement, number of unionized employees 10,000
Total number of employees | Unionized employees concentration risk  
Concentration Risk [Line Items]  
Concentration risk percentage 45.00%