Labor Union Contracts (Details)	3 Months Ended
Mar. 31, 2019 Employee
Concentration risk
Number of unionized employees (less than)	80
Total number of employees \| Unionized employees concentration risk
Concentration risk
Concentration risk, percent	26.00%
Workforce Subject to Collective Bargaining Arrangements Expiring within One Year \| Unionized employees concentration risk
Concentration risk
Concentration risk, percent	6.00%

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.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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