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Income Taxes (Narrative) (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2020 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2019 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2018 | Dec. 31, 2018
Income Taxes [Line Items] |  |  |  |  |  |  |  |  |
Effective income tax rate |  | 54.60% | 54.60% |  | 24.40% | 24.40% |  | 78.10% | 78.10%
Increase (Decrease) in Effective Tax Rate |  | 30.20% |  |  | 53.70% |  |  |  |
State regulatory proceedings, value | $ 0.0 |  |  | $ 9.5 |  |  | $ 127.8 |  |
Deferred Tax Assets, Operating Loss Carryforwards | 602.1 | $ 602.1 | $ 602.1 | 765.9 | $ 765.9 | $ 765.9 |  |  |
Deferred Tax Assets, Charitable Contribution Carryforwards | 7.8 | 7.8 | 7.8 |  |  |  |  |  |
Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions | 1.5 |  |  | 0.6 |  |  | 0.4 |  |
Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions | 0.0 |  |  | 22.6 |  |  | 0.2 |  |
Unrecognized Tax Benefits, Income Tax Penalties Expense | 0.0 |  |  | 0.0 |  |  | $ 0.0 |  |
Unrecognized Tax Benefits, Income Tax Penalties Accrued | 0.0 | 0.0 | 0.0 | $ 0.0 | $ 0.0 | $ 0.0 |  |  |
Deferred Tax Assets, Valuation Allowance | 6.4 | 6.4 | 6.4 |  |  |  |  |  |
Internal Revenue Service (IRS) |  |  |  |  |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |  |  |  |  |
Deferred Tax Assets, Operating Loss Carryforwards | 520.8 | 520.8 | 520.8 |  |  |  |  |  |
State and Local Jurisdiction |  |  |  |  |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |  |  |  |  |
Deferred Tax Assets, Operating Loss Carryforwards | $ 81.4 | $ 81.4 | $ 81.4 |  |  |  |  |  |

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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible charitable contribution carryforwards. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32632-109319 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32621-109319 + Details
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- Definition Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319 + Details
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- Definition Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to tax exempt income, equity in earnings (loss) of an unconsolidated subsidiary, minority noncontrolling interest income (loss), tax holiday, disposition of a business, disposition of an asset, repatriation of foreign earnings, repatriation of foreign earnings jobs creation act of 2004, increase (decrease) in enacted tax rate, prior year income taxes, increase (decrease) in deferred tax asset valuation allowance, and other adjustments. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319 + Details
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