Consolidated Statements of Income (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Revenues	$ 133,212	$ 117,540	$ 272,465	$ 229,924
Costs and expenses:
Cost of goods sold	91,904	88,688	190,203	177,663
Selling, general and administrative expenses	10,117	11,762	23,713	22,652
Environmental remediation charge	1,750	0	2,500	0
Total costs and expenses	103,771	100,450	216,416	200,315
Operating income	29,441	17,090	56,049	29,609
Interest expense, net	(5,667)	(6,277)	(12,003)	(12,763)
Income before income taxes	23,774	10,813	44,046	16,846
Income tax provision	(4,592)	(5,733)	(9,377)	(6,715)
Net income	$ 19,182	$ 5,080	$ 34,669	$ 10,131
Net income per share:
Basic (in dollars per share)	$ 0.47	$ 0.13	$ 0.86	$ 0.25
Diluted (in dollars per share)	$ 0.47	$ 0.13	$ 0.85	$ 0.25
Distributions per share (in dollars per share)	$ 0.31	$ 0.31	$ 0.62	$ 0.62
Weighted-average shares outstanding (in thousands):
Basic (in shares)	40,508,872	40,332,340	40,473,705	40,289,889
Diluted (in shares)	40,693,741	40,458,932	40,655,416	40,414,033