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v3.19.3.a.u2

Pension and Other Postretirement Benefits (Schedule of Total Expense for All Retirement Plans) (Details) $ in Thousands | 12 Months Ended
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Dec. 31, 2019 USD ($) plan | Dec. 31, 2018 USD ($) plan | Dec. 31, 2017 USD ($)
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total retirement plan expense | $ 2,960 | $ 2,927 | $ 3,044
Multiemployer plans withdrawal obligation | 4,200 |  |
401(k) plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total retirement plan expense | 2,419 | 2,262 | 2,248
Other Postretirement Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total retirement plan expense | 346 | 427 | 476
Multiemployer and other defined benefit and pension plans |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total retirement plan expense | $ 195 | $ 238 | $ 320
Number of plans | plan | 1 | 3 |
Multiemployer Plans Exited | Multiemployer and other defined benefit and pension plans |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Number of plans | plan | 2 |  |

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