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Fair Value Measurements - Change in the fair value of the derivative warrant liabilities (Details) - USD ($) | 3 Months Ended | 9 Months Ended
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Mar. 31, 2021 | Dec. 31, 2020 | Sep. 30, 2020
Change in the fair value of the derivative warrant liabilities |  |  |
Beginning balance at January 1 | $ 95,342,000 |  |
Change in fair value of warrants | 66,397,000 |  |
Ending balance at December 31 | 161,486,000 | $ 95,342,000 |
Star Peak Energy Transition Corp [Member] | Level 3 |  |  |
Change in the fair value of the derivative warrant liabilities |  |  |
Beginning balance at January 1 | 121,091,978 | 11,822,148 |
Issuance of derivative |  |  | $ 11,822,148
Change in fair value of warrants | 155,781,741 | 109,269,830 |
Ending balance at December 31 | $ 276,873,719 | $ 121,091,978 | $ 11,822,148

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- Definition Amount of gain (loss) recognized in income from liability measured at fair value on recurring basis using unobservable input (level 3). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details
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