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Employee Benefit Plans - Participation in Multiemployer Defined Benefit Pension Plan (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Defined Contribution Plan Disclosure [Line Items]      
Contributions $ 1,300 $ 1,500 $ 1,200
Multiemployer Plans, Pension      
Defined Contribution Plan Disclosure [Line Items]      
Contributions 11,347 12,586 12,638
Multiemployer Plans, Pension | Pension Trust Fund for Operating Engineers Pension Plan      
Defined Contribution Plan Disclosure [Line Items]      
Contributions 1,932 2,477 2,145
Multiemployer Plans, Pension | Laborers Pension Trust for Northern California      
Defined Contribution Plan Disclosure [Line Items]      
Contributions 880 953 1,059
Multiemployer Plans, Pension | Carpenter Funds Administrative Office      
Defined Contribution Plan Disclosure [Line Items]      
Contributions 748 727 636
Multiemployer Plans, Pension | Cement Mason Pension Trust Fund For Northern California      
Defined Contribution Plan Disclosure [Line Items]      
Contributions 504 423 311
Multiemployer Plans, Pension | All other funds      
Defined Contribution Plan Disclosure [Line Items]      
Contributions $ 7,283 $ 8,006 $ 8,487