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Accounting For Income Taxes - Additional Information (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Components of Income Tax Expense (Benefit) [Line Items] |  |  |  |
Federal statutory tax rate | 21.00% | 21.00% | 21.00% | 35.00%
State Tax Credit Carryforward [Member] |  |  |  |
Components of Income Tax Expense (Benefit) [Line Items] |  |  |  |
Tax credit carryforward, amount | $ 18.3 |  |  |
Tax credit carryforwards, net of valuation allowance | 8.6 |  |  |
Tax credit carryforward, valuation allowance | $ (9.7) |  |  |
Minimum [Member] | State Tax Credit Carryforward [Member] |  |  |  |
Components of Income Tax Expense (Benefit) [Line Items] |  |  |  |
Tax credit carryforward, expiration date | 2021 |  |  |
Maximum [Member] | State Tax Credit Carryforward [Member] |  |  |  |
Components of Income Tax Expense (Benefit) [Line Items] |  |  |  |
Tax credit carryforward, expiration date | 2034 |  |  |

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- Definition Percentage of domestic federal statutory tax rate applicable to pretax income (loss). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 6.I.Fact.4) -URI http://asc.fasb.org/extlink&oid=116825942&loc=d3e330036-122817 Reference 2: 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 The amount of the tax credit carryforward, before tax effects, available to reduce future taxable income under enacted tax laws. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32559-109319 + Details
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