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Retirement Benefits (Tables) | 12 Months Ended
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Dec. 31, 2020
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract] |
Schedule of Defined Contribution Plan | The following table presents our participation in these plans:
Pension Trust Fund | Pension Plan Employer Identification Number |  | Pension Protection Act (“PPA”) Certified Zone Status (1) |  | FIP / RP Status Pending/Implemented (2) |  | Contributions |  | Surcharge Imposed |  | Expiration Date of Collective Bargaining Agreement (3)
| 2020 |  | 2019 |  |  | 2020 |  | 2019 |  | 2018 |  |
Pension Trust Fund for Operating Engineers Pension Plan | 94-6090764 |  | Yellow |  | Yellow |  | Yes |  | $ | 2,278 |  |  | $ | 2,314 |  |  | $ | 1,932 |  |  | No |  | Various
Carpenter Funds Administrative Office | 94-6050970 |  | Red |  | Red |  | Yes |  | 915 |  | 547 |  | 748 |  | No |  | Various
Laborers Pension Trust for Northern California | 94-6277608 |  | Green |  | Green |  | Yes |  | 787 |  | 857 |  | 880 |  | No |  | Various
Cement Mason Pension Trust Fund For Northern California | 94-6277669 |  | Yellow |  | Yellow |  | Yes |  | 426 |  | 320 |  | 504 |  | No |  | Various
All other funds (4) |  |  |  |  |  |  |  |  | 7,571 |  | 7,144 |  | 7,283 |  |  |  |
|  |  |  |  | Total Contributions: |  | $ | 11,977 |  |  | $ | 11,182 |  |  | $ | 11,347 |  |  |  |  |
(1) The most recent PPA zone status available in 2020 and 2019 is for the plan’s year-end during 2019 and 2018, respectively. The zone status is based on information that we received from the plan and is certified by the plan’s actuary. Among other factors, plans in the red zone are generally less than 65 percent funded, plans in the orange zone are less than 80 percent funded and have an Accumulated Funding Deficiency in the current year or projected into the next six years, plans in the yellow zone are less than 80 percent funded and plans in the green zone are at least 80 percent funded. (2) Indicates whether the plan has a financial improvement plan (“FIP”) or a rehabilitation plan (“RP”) which is either pending or has been implemented. (3) Lists the expiration date(s) of the collective-bargaining agreement(s) to which the plans are subject. (4) These funds include multi-employer plans for pensions and other employee benefits. The total individually insignificant multi-employer pension costs contributed were $1,252, $829 and $1,300 for 2020, 2019 and 2018, respectively, and are included in the contributions to all other funds along with contributions to other types of benefit plans. Other employee benefits include certain coverage for medical, prescription drug, dental, vision, life and accidental death and dismemberment, disability and other benefit costs.

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