Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement of Comprehensive Income [Abstract]
Net Income	$ 19,144	$ 20,367
Other Comprehensive Income (Loss), net of tax:
Amortization of prior service cost, net of tax of $(8) and $(8), respectively	(11)	(12)
Net gain, net of tax of $77 and $67, respectively	93	101
Cash Flow Hedges, net of tax:
Unrealized gain on commodity contract cash flow hedges, net of tax of $192 and $0, respectively	338	0
Total Other Comprehensive Income	420	89
Comprehensive Income	$ 19,564	$ 20,456