Stockholder's Equity - Accumulated Other Comprehensive Income (Loss) - Changes in Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			$ (6,267)	$ (6,713)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			2,741	1,000
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			(936)	81
Net current-period other comprehensive income (loss)	$ 1,732	$ (2,008)	1,805	1,081
Ending balance	(4,462)	(5,747)	(4,462)	(5,747)
UnrealizedGainsLossesFromDefinedBenefitPensionAndPostretirementPlanItems [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			(4,933)	(5,928)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			132	213
Net current-period other comprehensive income (loss)			132	213
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings, Tax Effect				0
Ending balance	(4,801)	(5,715)	(4,801)	(5,715)
Accumulated (Gain) Loss from Commodity Contracts Cash Flows Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			(1,334)	(785)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			2,770	1,000
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			(1,060)	(132)
Net current-period other comprehensive income (loss)			1,710	868
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings, Tax Effect				(115)
Ending balance	376	$ (32)	376	(32)
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings, Tax Effect				$ (115)
Accumulated (Gain) Loss from Interest Rate Swap Cash Flows Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			(29)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			(8)
Net current-period other comprehensive income (loss)			(37)
Ending balance	$ (37)		$ (37)