Consolidated Statements of Income (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Revenues	$ 143,919	$ 133,212	$ 283,498	$ 272,465
Costs and expenses:
Cost of goods sold	101,849	91,904	200,442	190,203
Selling, general and administrative expenses	12,345	10,117	22,022	23,713
Environmental remediation charge	0	1,750	0	2,500
Total costs and expenses	114,194	103,771	222,464	216,416
Operating income	29,725	29,441	61,034	56,049
Interest expense, net	(5,509)	(5,667)	(10,969)	(12,003)
Income before income taxes	24,216	23,774	50,065	44,046
Income taxes	(7,946)	(4,592)	(13,445)	(9,377)
Net income	$ 16,270	$ 19,182	$ 36,620	$ 34,669
Net income per share:
Basic (in dollars per share)	$ 0.40	$ 0.47	$ 0.90	$ 0.86
Diluted (in dollars per share)	$ 0.40	$ 0.47	$ 0.90	$ 0.85
Distributions per share (in dollars per share)	$ 0.35	$ 0.31	$ 0.70	$ 0.62
Weighted average shares outstanding (in thousands):
Basic (in shares)	40,740,979	40,508,872	40,726,397	40,473,705
Diluted (in shares)	40,850,253	40,693,741	40,833,041	40,655,416