Employees Retirement Plans - Pension expense (Details) $ in Thousands |
12 Months Ended | ||
---|---|---|---|
Dec. 31, 2020
USD ($)
item
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Dec. 31, 2019
USD ($)
|
Dec. 31, 2018
USD ($)
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Employee Retirement Plans | |||
Number of regional multi-employer pension plans in which the entity participates | item | 44 | ||
Defined contribution plans | $ 10,251 | $ 10,015 | $ 7,595 |
Multi-employer plans | 11,754 | 13,241 | 11,224 |
Total expense related to participation in retirement plans | $ 22,005 | $ 23,256 | $ 18,819 |