Labor Union Contracts (Details)	6 Months Ended
Jun. 30, 2019 Employee
Concentration risk
Entity number of employees	43,000
Total number of employees \| Unionized employees concentration risk
Concentration risk
Concentration risk, percent	26.00%
Workforce Subject to Collective Bargaining Arrangements, Expired \| Unionized employees concentration risk
Concentration risk
Concentration risk, percent	3.00%
Workforce Subject to Collective Bargaining Arrangements Expiring within One Year \| Unionized employees concentration risk
Concentration risk
Concentration risk, percent	80.00%

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
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
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-Section 50
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6404-108592

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