Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
Net Income	$ 8,304	$ 6,387	$ 36,968	$ 33,241
Other Comprehensive Income (Loss), net of tax:
Amortization of prior service cost, net of tax of $(5), $(5), $(10) and $(11), respectively	(14)	(14)	(29)	(28)
Net gain, net of tax of $42, $41, $86 and $80, respectively	121	108	242	217
Cash Flow Hedges, net of tax:
Unrealized gain (loss) on commodity contract cash flow hedges, net of tax of $(850), $429, $343 and $(327), respectively	(2,115)	1,061	868	(728)
Total Other Comprehensive Income (Loss), net of tax	(2,008)	1,155	1,081	(539)
Comprehensive Income	$ 6,296	$ 7,542	$ 38,049	$ 32,702