Consolidated Condensed Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues	$ 575,336	$ 606,950	$ 570,289
Costs and expenses:
Cost of goods sold	470,037	429,789	408,772
Selling, general and administrative expenses	46,392	44,655	50,397
Environmental remediation charges	0	0	3,522
Total costs and expenses	516,429	474,444	462,691
Operating income	58,907	132,506	107,598
Interest expense, net	(32,761)	(22,909)	(23,132)
Income before income taxes	26,146	109,597	84,466
Income tax benefit (provision)	5,568	(19,687)	(13,885)
Net income	$ 31,714	$ 89,910	$ 70,581
Net income per share:
Basic (in dollars per share)	$ 0.78	$ 2.21	$ 1.74
Diluted (in dollars per share)	0.77	2.20	1.73
Distributions per share (in dollars per share)	$ 1.5	$ 1.425	$ 1.28