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Retirement Plans and Other Postretirement Benefits - Fair Value of Plan Assets (Details) - Defined Benefit Plan - USD ($) $ in Thousands | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
--- | --- | --- | --- | ---
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Total | $ 23,164 | $ 22,090 | $ 25,843 | $ 25,446
Fixed income funds |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Total | 11,116 | 11,003 |  |
Short-term investment funds |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Total | 951 | 800 |  |
Level 1 |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Total | 951 | 800 |  |
Level 1 | Fixed income funds |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Total | 0 | 0 |  |
Level 1 | Short-term investment funds |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Total | 951 | 800 |  |
Level 2 |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Total | 22,213 | 21,290 |  |
Level 2 | Fixed income funds |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Total | 11,116 | 11,003 |  |
Level 2 | Short-term investment funds |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Total | 0 | 0 |  |
Level 3 |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Total | 0 | 0 |  |
Level 3 | Fixed income funds |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Total | 0 | 0 |  |
Level 3 | Short-term investment funds |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Total | 0 | 0 |  |
United States | Equity security funds |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Total | 8,883 | 8,198 |  |
United States | Level 1 | Equity security funds |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Total | 0 | 0 |  |
United States | Level 2 | Equity security funds |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Total | 8,883 | 8,198 |  |
United States | Level 3 | Equity security funds |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Total | 0 | 0 |  |
International | Equity security funds |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Total | 2,214 | 2,089 |  |
International | Level 1 | Equity security funds |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Total | 0 | 0 |  |
International | Level 2 | Equity security funds |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Total | 2,214 | 2,089 |  |
International | Level 3 | Equity security funds |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Total | $ 0 | $ 0 |  |

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