Commitments and Contingencies - Additional Information (Detail) - USD ($)	3 Months Ended
Mar. 31, 2021	Dec. 31, 2020
Commitments and Contingencies Additional Textual [Abstract]
Remaining environmental accrued liability recorded	$ 0	$ 0
Commitment fee expense	400,000
Commitment fee expense accrual	700,000
Beta's decommissioning obligations, full supported by surety bonds	161,300,000
Beta's decommissioning obligations, cash	$ 300,000

Carrying value of the obligation (known or estimated) arising from requirements to perform activities to remediate one or more sites, payable in twelve months or in the next operating cycle if longer.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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-Name Accounting Standards Codification
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-Name Accounting Standards Codification
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