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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 | 9 Months Ended
--- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024
Amortization of: |  |  |  |
Portion of costs (credits) charged to expense | $ (2,777) | $ (12,188) | $ (9,427) | $ (36,633)
Pension Plans |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Service cost-benefits earned during the period | 11,038 | 10,910 | 33,114 | 32,731
Non-service costs (credits): |  |  |  |
Interest cost on benefit obligation | 38,780 | 37,161 | 116,340 | 111,482
Expected return on plan assets | (44,698) | (47,163) | (134,094) | (141,488)
Amortization of: |  |  |  |
Prior service credit | 0 | 0 | 0 | 0
Net actuarial loss (gain) | 11,683 | 10,479 | 35,049 | 31,437
Net periodic benefit costs (credits) | 16,803 | 11,387 | 50,409 | 34,162
Portion of costs (credits) charged to expense | 10,270 | 5,828 | 30,096 | 17,665
Other Benefits Plans |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Service cost-benefits earned during the period | 2,020 | 2,489 | 6,061 | 7,466
Non-service costs (credits): |  |  |  |
Interest cost on benefit obligation | 5,086 | 5,542 | 15,258 | 16,627
Expected return on plan assets | (12,142) | (11,709) | (36,426) | (35,126)
Amortization of: |  |  |  |
Prior service credit | 0 | (9,447) | (1,265) | (28,341)
Net actuarial loss (gain) | (2,932) | (2,169) | (8,796) | (6,507)
Net periodic benefit costs (credits) | (7,968) | (15,294) | (25,168) | (45,881)
Portion of costs (credits) charged to expense | $ (6,110) | $ (11,396) | $ (19,382) | $ (34,217)

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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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