Labor Union Contracts (Details)	6 Months Ended
Jun. 30, 2018
Unionized employees concentration risk \| Total number of employees
Concentration Risk [Line Items]
Concentration risk percentage	44.00%

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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