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Income Taxes - Significant Components of our deferred tax assets & liabilities (Details) - USD ($) $ in Millions | Dec. 31, 2024 | Dec. 31, 2023
--- | --- | ---
Deferred tax assets: |  |
Accrued postretirement benefit cost | $ 30.1 | $ 30.7
Net operating losses | 473.3 | 467.6
Disallowed interest expense | 37.1 | 29.2
Derivative and hedging contracts | 0.1 | 1.2
Fixed asset tax over book basis | 0.0 | 9.2
Other | 29.4 | 28.3
Total deferred tax assets | 570.0 | 566.2
Valuation allowance | (504.4) | (537.6)
Net deferred tax assets | 65.6 | 28.6
Deferred tax liabilities: |  |
Fixed asset book over tax basis | (115.9) | (62.0)
Derivatives | 0.0 | 0.0
Foreign basis differences | 0.6 | (18.1)
Other | (21.4) | (20.6)
Total deferred tax liabilities | (136.7) | (100.7)
Net deferred tax liability | $ (71.1) | $ (72.1)

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