Stockholder's Equity - Accumulated Other Comprehensive Income (Loss) - Changes in Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (6,713)	$ (4,272)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	3,021	(2,232)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	68	538
Net current-period other comprehensive income (loss)	3,089	(1,694)
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings, Tax Effect		0
Ending balance	(3,739)	(6,873)
UnrealizedGainsLossesFromDefinedBenefitPensionAndPostretirementPlanItems [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(5,928)	(4,743)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	107	94
Net current-period other comprehensive income (loss)	107	94
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings, Tax Effect		(1,022)
Ending balance	(5,821)	(5,671)
Accumulated (Gain) Loss from Commodity Contracts Cash Flows Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(785)	471
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	3,021	(2,232)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(39)	444
Net current-period other comprehensive income (loss)	2,982	(1,788)
Prior Period Reclassification Adjustment	(115)
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings, Tax Effect		115
Ending balance	2,082	(1,202)
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Prior Period Reclassification Adjustment	$ (115)
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings, Tax Effect		$ (907)