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Pension and Savings Plans (Tables) | 12 Months Ended
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Dec. 31, 2025
Pension and Savings Plans [Abstract] |
Schedule of fair value of assets by asset category and by fair value hierarchy | The following tables present the fair value of assets in the Master Trust by asset category and by fair value hierarchy:
| December 31, 2025
| Level 1 |  | Level 2 |  | Level 3 |  | Total
| (Dollars in millions)
Corporate bonds | $ | — |  |  | $ | 60.3 |  |  | $ | — |  |  | $ | 60.3 |
U.S. government securities | 16.1 |  |  | 3.2 |  |  | — |  |  | 19.3 |
Other | 6.1 |  |  | 2.4 |  |  | — |  |  | 8.5 |
Total assets at fair value | $ | 22.2 |  |  | $ | 65.9 |  |  | $ | — |  |  | 88.1 |
Assets measured at net asset value practical expedient (1) |  |  |  |  |  |  |
Private mutual funds |  |  |  |  |  |  | 18.4 |
Total plan assets |  |  |  |  |  |  | $ | 106.5 |
| December 31, 2024
| Level 1 |  | Level 2 |  | Level 3 |  | Total
| (Dollars in millions)
Corporate bonds | $ | — |  |  | $ | 65.3 |  |  | $ | — |  |  | $ | 65.3 |
U.S. government securities | 13.7 |  |  | 3.4 |  |  | — |  |  | 17.1 |
Other | 4.3 |  |  | 1.9 |  |  | — |  |  | 6.2 |
Total assets at fair value | $ | 18.0 |  |  | $ | 70.6 |  |  | $ | — |  |  | 88.6 |
Assets measured at net asset value practical expedient (1) |  |  |  |  |  |  |
Private mutual funds |  |  |  |  |  |  | 16.2 |
Total plan assets |  |  |  |  |  |  | $ | 104.8 |
(1) In accordance with Accounting Standards Update 2015-07, investments that are measured at fair value using the net asset value per share practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in the tables are intended to permit reconciliation of the fair value hierarchy to the total value of assets of the plans.

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- Definition Pension and Savings Plans [Abstract] + References No definition available. + Details
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- Definition Tabular disclosure of the major categories of plan assets of pension plans and/or other employee benefit plans. This information may include, but is not limited to, the target allocation of plan assets, the fair value of each major category of plan assets, and the level within the fair value hierarchy in which the fair value measurements fall. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 715 -SubTopic 20 -Subparagraph (d)(5) -Name Accounting Standards Codification -Paragraph 1 -Section 50 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 + Details
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