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Commitments - Narrative (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Commitments [Line Items] |  |  |
Percentage decrease in future demand reservation fees | 50.00% |  |
Percentage decrease in future demand reservation volume | 35.00% |  |
Maximum annual contributions per employee (401K Plan) | 100.00% |  |
Minimum matching employer contribution for 401K | 50.00% |  |
Cost recognized on defined contribution plan | $ 2.6 | $ 2.9 | $ 2.6
Minimum |  |  |
Commitments [Line Items] |  |  |
Minimum matching employer contribution for 401K | 4.00% |  |
Maximum |  |  |
Commitments [Line Items] |  |  |
Minimum matching employer contribution for 401K | 6.00% |  |

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- Definition Firm Transportation Agreements, Required Reduction In Future Demand Reservation Fees, Percentage + References No definition available. + Details
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- Definition Amount of cost for defined contribution plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942 + Details
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- Definition Maximum percentage of employee gross pay the employee may contribute to a defined contribution plan. + References No definition available. + Details
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