Stockholders' Equity Accumulated Other comprehensive Income (Loss) - Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), after Tax [Roll Forward]
Accumulated other comprehensive loss at beginning of period	$ (5,840)	$ (5,676)
Other Comprehensive Income (Loss), before Reclassifications, before Tax	508	(636)
Amounts reclassified from accumulated other comprehensive loss	454	472
Net current-period other comprehensive income	962	(164)
Unrealized gain (loss) on commodity contract cash flow hedges, net of tax of $496, $(150) and $(22), respectively	742	(227)	$ (33)
Accumulated other comprehensive loss at end of period	(4,878)	(5,840)	(5,676)
UnrealizedGainsLossesFromDefinedBenefitPensionAndPostretirementPlanItems [Member]
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), after Tax [Roll Forward]
Accumulated other comprehensive loss at beginning of period	(5,580)	(5,643)
Other Comprehensive Income (Loss), before Reclassifications, before Tax	(254)	(286)
Amounts reclassified from accumulated other comprehensive loss	474	349
Net current-period other comprehensive income	220	63
Accumulated other comprehensive loss at end of period	(5,360)	(5,580)	(5,643)
Accumulated (Gain) Loss from Commodity Contracts Cash Flows Hedges [Member]
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), after Tax [Roll Forward]
Accumulated other comprehensive loss at beginning of period	(260)	(33)
Other Comprehensive Income (Loss), before Reclassifications, before Tax	762	(350)
Amounts reclassified from accumulated other comprehensive loss	(20)	123
Net current-period other comprehensive income		(227)
Accumulated other comprehensive loss at end of period	$ 482	$ (260)	$ (33)