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Benefit Plans and Other Postretirement Benefits, Multiemployer Plans (Details)
$ in Thousands
12 Months Ended
Dec. 31, 2016
USD ($)
Employer
Dec. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
Multiemployer Plans [Abstract]      
Number of employers that must be exceeded during a given period in order for certain union workers to participate in multiemployer plans | Employer 1    
Multiemployer Pension Plans      
Multiemployer Plans [Abstract]      
Multiemployer contributions | $ $ 707 $ 944 $ 156