Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Comprehensive Income [Abstract]
Net Income	$ 20,367	$ 21,109
Other Comprehensive Income (Loss), net of tax:
Amortization of prior service cost, net of tax of $(8) and $(7), respectively	(12)	(10)
Net gain, net of tax of $67 and $62, respectively	101	92
Cash Flow Hedges, net of tax:
Unrealized loss on commodity contract cash flow hedges, net of tax of $- and $17, respectively	0	26
Total Other Comprehensive Income	89	108
Comprehensive Income	$ 20,456	$ 21,217