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Retirement Plans And Other Postretirement Benefits (Narrative) (Details) $ in Thousands | 12 Months Ended
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Dec. 31, 2019 USD ($) employee | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($)
Defined Benefit Plan Disclosure [Line Items] |  |  |
Pension and other postretirement liabilities | $ 107,446 | $ 88,124 |
Percentage of change in health care cost trend rate assumptions would be immaterial | 1.00% |  |
Expected pension expense for next twelve months | $ 14,200 |  |
Term of estimated benefit payments for fixed income securities, minimum | 1 year |  |
Term of estimated benefit payments for fixed income securities, maximum | 2 years |  |
Defined benefit, average remaining duration of benefit payments for pension plans | 11 years 219 days |  |
Pension and Other Postretirement Benefits Cost (Reversal of Cost) | $ 9,642 | 10,406 | $ 10,193
Unfunded Non-Qualified Supplemental Pension Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Projected benefit obligation to unfunded plan | 2,200 | 2,000 |
Pension and Other Postretirement Benefits Cost (Reversal of Cost) | $ 100 | 100 | 100
Films Manufacturing Facility In Kerkrade | Multiemployer Plan, Individually Insignificant Multiemployer Plans [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Number of employees participating in pension plan | employee | 70 |  |
Multi-employer pension plan, pension expenses | $ 300 | 400 | 400
Pension Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Prior service cost (benefit) | 0 |  |
Projected benefit obligation to unfunded plan | 318,763 | 287,240 | 318,123
Multi-employer pension plan, pension expenses | 9,585 | $ 10,342 | $ 10,134
Credit Spread Over London Interbank Offered Rate Basis Points | $ 12,300 |  |

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