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Employee Benefit Plans (Plan Contributions) (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Multiemployer Plans [Line Items]      
Company contributions $ 4,556 $ 4,078 $ 3,885
Western Conference of Teamsters Pension Trust [Member]      
Multiemployer Plans [Line Items]      
EIN/Pension plan number 916145047    
Pension Protection Act zone status [1] Green Green  
Company contributions $ 4,314 $ 3,852 3,662
Collective-bargaining agreement, expiration date, start Apr. 30, 2016    
Collective-bargaining agreement, expiration date, end Dec. 31, 2019    
Locals 302 & 612 of the IOUE - Employers Construction Industry Retirement Plan [Member]      
Multiemployer Plans [Line Items]      
EIN/Pension plan number 916028571    
Pension Protection Act zone status [1] Green Green  
Company contributions $ 242 $ 226 $ 223
Collective-bargaining agreement, expiration date Sep. 30, 2016    
[1] The most recent Pension Protection Act zone status available in 2015 and 2014 is for the plans' years ended December 31, 2014 and 2013, respectively.