Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net Income	$ 65,153	$ 56,580	$ 58,124
Employee Benefits, net of tax:
Amortization of prior service cost, net of tax of $(20), $(22) and $(31), respectively	(57)	(55)	(46)
Net gain(loss), net of tax of $368, $(49), and $432, respectively	1,052	(108)	663
Cash Flow Hedges, net of tax:
Unrealized (loss) on commodity contract cash flow hedges, net of tax of $(176), $(555) and $(8), respectively	(434)	(1,371)	(11)
Total Other Comprehensive Income (Loss)	561	(1,534)	606
Comprehensive Income	$ 65,714	$ 55,046	$ 58,730