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Pension Plans and Postretirement Benefits - Summary of Additional Information (Detail) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019
Pension Plan |  |
Pension Plans, Postretirement and Other Employee Benefits [Line Items] |  |
Decrease in accumulated other comprehensive income due to actuarial losses – before taxes | $ (2,333) | $ (5,523)
Other Benefits |  |
Pension Plans, Postretirement and Other Employee Benefits [Line Items] |  |
Decrease in accumulated other comprehensive income due to actuarial losses – before taxes | $ 0 | $ 0

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- Definition Pension Plans, Postretirement and Other Employee Benefits [Line Items] + References No definition available. + Details
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- Definition Amount, before tax, of gain (loss) for (increase) decrease in value of benefit obligation for change in actuarial assumptions and increase (decrease) in value of plan assets from experience different from that assumed of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=121641772&loc=SL7669646-108580 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=121641772&loc=d3e637-108580 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
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