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Pension Plans and Other Postretirement Benefits - Fair Value of Plan Assets (Details) - Defined Benefit Plan - USD ($) $ in Thousands | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
--- | --- | --- | ---
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total | $ 22,090 | $ 25,843 | $ 25,446
Fixed income funds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total | 11,003 | 12,165 |
Short-term investment funds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total | 800 | 588 |
Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total | 800 | 588 |
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 | 800 | 588 |
Level 2 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total | 21,290 | 25,255 |
Level 2 | Fixed income funds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total | 11,003 | 12,165 |
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 | 8,198 | 10,517 |
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 | 8,198 | 10,517 |
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 | 2,089 | 2,573 |
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 | 2,089 | 2,573 |
International | Level 3 | Equity security funds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total | $ 0 | $ 0 |

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition Amount of plan asset for defined benefit plan with accumulated benefit obligation in excess of plan assets. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e2417-114920 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e2417-114920 + Details
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