Commitments and Contingencies - Additional Information (Detail) - USD ($)	3 Months Ended
Mar. 31, 2020	Dec. 31, 2019
Commitments and Contingencies Additional Textual [Abstract]
Remaining environmental accrued liability recorded	$ 0	$ 0
Beta's decommissioning obligations, supported by surety bonds	161,300,000
Beta's decommissioning obligations, cash	300,000
Commitment fee expense	200,000
Commitment fee expense accrual	$ 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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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