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Retirement Plans and Other Postretirement Benefits - Schedule of Net Periodic Benefit Costs and Portion including Portion Charged to Expense (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2026 | Jun. 30, 2025 | Jun. 30, 2026 | Jun. 30, 2025
Amortization of: |  |  |  |
Portion of costs (credits) charged to expense | $ (5,018) | $ (3,692) | $ (9,000) | $ (6,650)
Pension Plans |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Service cost-benefits earned during the period | 11,684 | 11,127 | 23,783 | 22,076
Non-service costs (credits): |  |  |  |
Interest cost on benefit obligation | 37,292 | 38,584 | 74,904 | 77,560
Expected return on plan assets | (44,365) | (44,849) | (88,461) | (89,396)
Amortization of: |  |  |  |
Prior service cost (credit) | 151 | 0 | 302 | 0
Net actuarial loss (gain) | 10,443 | 11,248 | 21,596 | 23,366
Net periodic benefit costs (credits) | 15,205 | 16,110 | 32,124 | 33,606
Portion of costs (credits) charged to expense | 8,262 | 9,365 | 17,780 | 19,826
Other Benefits Plans |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Service cost-benefits earned during the period | 2,140 | 2,059 | 4,377 | 4,041
Non-service costs (credits): |  |  |  |
Interest cost on benefit obligation | 4,931 | 5,070 | 9,910 | 10,172
Expected return on plan assets | (12,719) | (12,142) | (25,438) | (24,284)
Amortization of: |  |  |  |
Prior service cost (credit) | 0 | 0 | 0 | (1,265)
Net actuarial loss (gain) | (2,746) | (2,965) | (5,446) | (5,864)
Net periodic benefit costs (credits) | (8,394) | (7,978) | (16,597) | (17,200)
Portion of costs (credits) charged to expense | $ (6,644) | $ (6,399) | $ (13,153) | $ (13,272)

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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 -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 17 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480482/715-20-55-17 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 45 -Paragraph 3A -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480535/715-20-45-3A Reference 3: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 18 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480482/715-20-55-18 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (h)(3) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (a)(3) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-6 + Details
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