CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Revenues:
Revenue - third parties	$ 105,927	$ 88,446
Revenue - affiliates	135	251
Total revenue	106,062	88,697
Costs and expenses:
Cost of sales (excluding depreciation and amortization expense) - affiliates	47,052	44,113
Depreciation and amortization	22,706	20,362
Long-lived asset impairment	1,540	805
Selling, general and administrative - affiliates	12,607	12,222
Interest expense	7,424	5,882
Other (income) expense, net	(407)	527
Total costs and expenses	90,922	83,911
Income before income taxes	15,140	4,786
Provision for income taxes	407	281
Net income	14,733	4,505
General partner interest in net income	1,772	1,095
Common units interest in net income	$ 12,961	$ 3,410
Weighted average common units outstanding:
Basic (in units)	42,278	38,670
Diluted (in units)	42,283	38,674
Income per common unit:
Basic (in dollars per unit)	$ 0.31	$ 0.09
Diluted (in dollars per unit)	$ 0.31	$ 0.09
Distributions declared and paid per limited partner unit (in dollars per unit)	$ 0.5125	$ 0.4925