Consolidated Statements of Income (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Revenues	$ 157,869	$ 151,911	$ 430,334	$ 381,835
Costs and expenses:
Cost of goods sold	112,499	109,806	302,702	287,469
Selling, general and administrative expenses	13,444	13,342	37,157	35,994
Environmental remediation charge	1,022	0	3,522	0
Total costs and expenses	126,965	123,148	343,381	323,463
Operating income	30,904	28,763	86,953	58,372
Interest expense, net	(5,556)	(6,280)	(17,559)	(19,043)
Income before income taxes	25,348	22,483	69,394	39,329
Income tax provision	(3,157)	(3,884)	(12,534)	(10,599)
Net income	$ 22,191	$ 18,599	$ 56,860	$ 28,730
Net income per share:
Basic (in dollars per share)	$ 0.55	$ 0.46	$ 1.40	$ 0.71
Diluted (in dollars per share)	$ 0.54	$ 0.46	$ 1.40	$ 0.71
Distributions per share (in dollars per share)	$ 0.31	$ 0.31	$ 0.93	$ 0.93
Weighted-average shares outstanding (in thousands):
Basic (in shares)	40,530,393	40,356,512	40,492,901	40,316,957
Diluted (in shares)	40,720,058	40,571,068	40,686,166	40,503,158