Income Taxes: Deferred Income Tax Assets and Liabilities (Details) - USD ($) $ in Millions |
Dec. 31, 2025 |
Dec. 31, 2024 |
|---|---|---|
| Deferred Tax Assets, Net [Abstract] | ||
| Regulatory liabilities | $ 68.5 | $ 70.9 |
| State tax credits | 8.1 | 8.4 |
| Federal NOL | 79.8 | 114.9 |
| State NOL | 8.1 | 12.4 |
| Partnership | 9.9 | 11.6 |
| Credit Carryovers (net of discount) | 104.1 | 109.5 |
| Other deferred tax assets | 40.2 | 35.4 |
| Total deferred tax assets | 318.7 | 363.1 |
| Deferred tax liabilities: | ||
| Accelerated depreciation, amortization and other plant-related differences | (753.7) | (729.2) |
| Regulatory assets | (39.8) | (49.5) |
| Goodwill | (84.0) | (75.9) |
| State deferred tax liability | (88.9) | (88.7) |
| Other deferred tax liabilities | (50.2) | (44.9) |
| Total deferred tax liabilities | (1,016.6) | (988.2) |
| Net deferred tax liability | $ (697.9) | $ (625.1) |
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- Definition Amount of deferred tax liabilities attributable to taxable temporary differences from state taxes. No definition available.
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- Definition Amount of deferred tax liability attributable to taxable temporary differences. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from investments (excludes investments in subsidiaries and equity method investments). Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition Amount after allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- References No definition available.
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible state and local operating loss carryforwards. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition Amount, before allocation of valuation allowance, of deferred tax asset attributable to deductible temporary differences, classified as other. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences derived regulatory assets and liabilities. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition Amount, before allocation of a valuation allowances, of deferred tax assets attributable to deductible tax credit carryforwards including, but not limited to, research, foreign, general business, alternative minimum tax, and other deductible tax credit carryforwards. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition Amount, before allocation of valuation allowance, of deferred tax asset attributable to deductible tax credit carryforwards, classified as other. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition Amount, after deferred tax asset, of deferred tax liability attributable to taxable differences without jurisdictional netting. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition Amount of deferred tax liability attributable to taxable temporary differences from goodwill. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- References No definition available.
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- Definition Amount of deferred tax liability attributable to taxable temporary differences classified as other. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition Amount of deferred tax liability attributable to taxable temporary differences from property, plant, and equipment. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition Amount of deferred tax liability attributable to taxable temporary differences from regulatory assets. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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