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Retirement Plans (Narrative) (Details) | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2021 USD ($) plan | Jun. 30, 2020 USD ($) | Jun. 30, 2021 USD ($) plan | Jun. 30, 2020 USD ($)
UNITED STATES |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Number of plans | plan | 3 |  | 3 |
Net periodic pension cost (income) | $ 100,000 | $ 100,000 | $ 100,000 | $ 100,000
UK Plan | United Kingdom Subsidiary [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Contributions to defined benefit pension plans |  |  | 2,500,000 |
Anticipated additional contribution | 2,500,000 |  | 2,500,000 |
Net periodic pension cost (income) | $ (951,000) | $ (785,000) | $ (1,894,000) | $ (1,591,000)

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