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v3.21.2

Components of Retirement Plan Costs (Detail) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020
Pension Plans |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Service Cost | $ 868 | $ 829 | $ 2,604 | $ 2,491
Interest Cost | 1,250 | 1,445 | 3,752 | 4,332
Expected Return on Plan Assets | (2,422) | (2,254) | (7,268) | (6,764)
Prior Service Cost Amortization | 76 | 80 | 226 | 240
Actuarial Loss Amortization | 2,021 | 1,618 | 6,065 | 4,854
Sub-total | 1,793 | 1,718 | 5,379 | 5,153
Amounts Capitalized and Deferred | (944) | (861) | (2,544) | (2,298)
Net Periodic Benefit Cost Recognized | 849 | 857 | 2,835 | 2,855
Other Postretirement Benefit Plans, Defined Benefit |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Service Cost | 759 | 673 | 2,275 | 2,023
Interest Cost | 685 | 782 | 2,055 | 2,341
Expected Return on Plan Assets | (627) | (515) | (1,881) | (1,547)
Prior Service Cost Amortization | 302 | 301 | 906 | 907
Actuarial Loss Amortization | 260 | 187 | 784 | 559
Sub-total | 1,379 | 1,428 | 4,139 | 4,283
Amounts Capitalized and Deferred | (904) | (860) | (2,358) | (2,087)
Net Periodic Benefit Cost Recognized | 475 | 568 | 1,781 | 2,196
Supplemental Employee Retirement Plans, Defined Benefit |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Service Cost | 89 | 70 | 266 | 212
Interest Cost | 114 | 137 | 343 | 412
Prior Service Cost Amortization | 14 | 15 | 42 | 43
Actuarial Loss Amortization | 372 | 259 | 1,117 | 777
Sub-total | 589 | 481 | 1,768 | 1,444
Amounts Capitalized and Deferred | (178) | (144) | (534) | (434)
Net Periodic Benefit Cost Recognized | $ 411 | $ 337 | $ 1,234 | $ 1,010

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- Definition Amount of expected return (loss) recognized in net periodic benefit (cost) credit, calculated based on expected long-term rate of return and market-related value of plan assets of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=123450688&loc=d3e4179-114921 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 18 -URI http://asc.fasb.org/extlink&oid=123450688&loc=d3e4587-114921 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(3) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 45 -Paragraph 3A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123453770&loc=SL108413299-114919 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e2709-114920 + Details
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