Summary of Significant Accounting Policies - Collective Bargaining Agreements (Details) |
Dec. 31, 2017 |
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| Accounting Policies [Abstract] | |
| Percentage of employees covered by collective bargaining agreements | 26.90% |
| Percentage of employees subject to collective bargaining agreements | 18.40% |
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- References No definition available.
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- Definition Percentage of employee participants subject to a collective bargaining arrangement to all of the employer's participants in a pension or postretirement benefit 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. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
- Definition Percentage of employee participants subject to a collective bargaining arrangement to all participants in a pension or postretirement benefit 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. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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