Stockholder's Equity - Accumulated Other Comprehensive Income (Loss) - Changes in Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), after Tax [Roll Forward]
Beginning balance	$ (4,878)	$ (5,840)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	1,269	(283)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(849)	372
Net current-period other comprehensive income (loss)	420	89
Ending balance	(4,458)	(5,751)
UnrealizedGainsLossesFromDefinedBenefitPensionAndPostretirementPlanItems [Member]
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), after Tax [Roll Forward]
Beginning balance	(5,360)	(5,580)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(9)	0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	91	89
Net current-period other comprehensive income (loss)	82	89
Ending balance	(5,278)	(5,491)
Accumulated (Gain) Loss from Commodity Contracts Cash Flows Hedges [Member]
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), after Tax [Roll Forward]
Beginning balance	482	(260)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	1,278	(283)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(940)	283
Net current-period other comprehensive income (loss)	338	0
Ending balance	$ 820	$ (260)