Stockholder's Equity - Accumulated Other Comprehensive Income (Loss) - Changes in Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 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	313	641
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(694)	170
Net current-period other comprehensive income (loss)	(381)	811
Ending balance	(5,259)	(5,029)
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)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	271	263
Net current-period other comprehensive income (loss)	262	263
Ending balance	(5,098)	(5,317)
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	322	641
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(965)	(93)
Net current-period other comprehensive income (loss)	(643)	548
Ending balance	$ (161)	$ 288