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Retirement Benefit Plans (Narrative) (Details) $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2019 USD ($) subsidiary employee plan | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($) | Feb. 03, 2006 plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |
Number of non-contributory defined benefit pension plans | plan |  |  |  |  | 2
Estimate of amount of unrecognized actuarial expense | $ 508 |  |  |  |
Number of defined contribution plans | plan | 2 |  |  |  |
IAM Plan |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |
Annual contribution amount | $ 557 | $ 418 | $ 408 |  |
Pension Plan |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |
Underfunded status | (1,844) | (1,944) |  |  |
Supplemental Employee Retirement Plan |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |
Estimate of amount of unrecognized actuarial expense | $ 475 |  |  |  |
SERP credited service period | 10 years |  |  |  |
Percentage of final 3 year average salary in which retirement benefit is based (percentage) | 20.00% |  |  |  |
Number of final years in which the Retirement Benefit is based | 3 years |  |  |  |
Retirement age | 65 years |  |  |  |
Period of time that vested retirement benefit will be paid after death or change in control | 90 days |  |  |  |
Years of monthly installments associated with SERP disability | 15 years |  |  |  |
Supplemental Employee Retirement Plan | Minimum |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |
Current retirement benefit percentage | 10.00% |  |  |  |
Supplemental Employee Retirement Plan | Maximum |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |
Current retirement benefit percentage | 20.00% |  |  |  |
Employees’ Retirement Plan |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |
Former employees | employee | 245 |  |  |  |
Current employees | employee | 64 |  |  |  |
Hourly Employees’ Pension Plan | Pension Plan |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |
Amount of final contribution |  |  |  | $ 622 |
Amount expenses of accumulated pension actuarial losses |  |  |  | $ 2,889 |
United States |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |
Annual contribution amount | $ 2,806 | 2,340 | 1,942 |  |
Foreign Plan |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |
Annual contribution amount | $ 861 | $ 850 | $ 716 |  |
Number of international subsidiaries that participate in defined contribution and savings plan | subsidiary | 3 |  |  |  |
Foreign Plan | Minimum |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |
Employer contribution percentage | 0.00% |  |  |  |
Foreign Plan | Maximum |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |
Employer contribution percentage | 10.00% |  |  |  |

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