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Amount of expense (income) related to adjustment to fair value of warrant liability.

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Amount of transfers of assets measured on a recurring basis out of Level 2 of the fair value hierarchy into Level 1.

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Fair value of asset after deduction of liability.

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Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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The fair value of shares that would be issued, determined under the conditions specified in the contract if the settlement were to occur at the reporting date.

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Fair Value Measurements - Financial assets that are measured at fair value on a recurring basis (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Sep. 30, 2020
Liabilities:
Change in fair value of warrant liabilities	$ 66,397,000	$ (1,009,000)	$ 84,455,000	$ (1,493,000)
Star Peak Energy Transition Corp [Member]
Liabilities:
Fair value of warrants	276,873,719		121,091,978		$ 11,822,148
Transfer of assets from level 1 to level 2	0		0
Transfer of assets from level 2 to level 1	0		0
Transfers to / from Level 3	0		0
Change in fair value of warrant liabilities	155,781,741	$ 0	(109,269,830)
Star Peak Energy Transition Corp [Member] \| Recurring
Liabilities:
Fair value of warrants			121,091,978
Total fair value	660,459,452		504,813,725
Star Peak Energy Transition Corp [Member] \| Recurring \| Public warrants
Liabilities:
Fair value of warrants	171,878,063		64,339,997
Star Peak Energy Transition Corp [Member] \| Recurring \| Private warrants
Liabilities:
Fair value of warrants	104,995,656		56,751,981
Star Peak Energy Transition Corp [Member] \| Recurring \| U.S. Treasury Securities
Assets:
Investments held in Trust Account	383,585,733		383,721,747
Liabilities:
Total fair value			504,813,725
Star Peak Energy Transition Corp [Member] \| Recurring \| Level 1
Liabilities:
Total fair value	555,463,796		448,061,744
Star Peak Energy Transition Corp [Member] \| Recurring \| Level 1 \| Public warrants
Liabilities:
Fair value of warrants	171,878,063		64,339,997
Star Peak Energy Transition Corp [Member] \| Recurring \| Level 1 \| U.S. Treasury Securities
Assets:
Investments held in Trust Account	383,585,733		383,721,747
Liabilities:
Total fair value			383,721,747
Star Peak Energy Transition Corp [Member] \| Recurring \| Level 3
Liabilities:
Fair value of warrants			121,091,978
Total fair value	104,995,656		56,751,981
Star Peak Energy Transition Corp [Member] \| Recurring \| Level 3 \| Private warrants
Liabilities:
Fair value of warrants	$ 104,995,656		56,751,981
Star Peak Energy Transition Corp [Member] \| Recurring \| Level 3 \| U.S. Treasury Securities
Liabilities:
Total fair value			$ 121,091,978