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Employee Benefit Plans - Participation in Multiemployer Defined Benefit Pension Plan (Details) - USD ($) $ in Thousands | 12 Months Ended
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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

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