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.

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Commitments and Contingencies - Additional Information (Detail) - USD ($)			6 Months Ended
	Jun. 24, 2019	Mar. 12, 2017	Jun. 30, 2019	Dec. 31, 2018
Commitments and Contingencies Additional Textual [Abstract]
Remaining environmental accrued liability recorded			$ 0	$ 0
Beta's decommissioning obligations, previously supported by surety bonds			71,300,000
Beta's decommissioning obligations, cash			90,200,000
Proceeds from Beta Decommissioning Trust account	$ 90,000,000		0
Beta's decommissioning obligations, full supported by surety bonds			161,300,000
Beta's decommissioning remaining obligations, cash			$ 300,000
Environmental Protection Agency [Member]
Commitments and Contingencies Additional Textual [Abstract]
Final date to close outstanding environmental related issues		Jun. 30, 2018