CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues:
Revenue - third parties	$ 580,739	$ 465,744	$ 386,731
Revenue - affiliates	297	449	762
Total revenue	581,036	466,193	387,493
Costs and expenses:
Cost of sales (excluding depreciation and amortization expense) - affiliates	238,038	202,045	183,160
Depreciation and amortization	128,196	103,711	88,298
Long-lived asset impairment	12,810	5,350	29,560
Restructuring charges	702
Selling, general and administrative - affiliates	80,521	61,971	49,889
Interest expense	57,811	37,068	25,167
Other (income) expense, net	(74)	(9,481)	(35)
Total costs and expenses	518,004	400,664	376,039
Income before income taxes	63,032	65,529	11,454
Provision for income taxes	1,313	1,506	945
Net income	61,719	64,023	10,509
General partner interest in net income	13,240	7,969	4,623
Common units interest in net income	$ 48,479	$ 56,054	$ 5,886
Weighted average common units outstanding used in income per common unit:
Basic (in units)	54,107	47,651	41,371
Diluted (in units)	54,109	47,667	41,382
Income per common unit:
Basic (in dollars per unit)	$ 0.89	$ 1.18	$ 0.14
Diluted (in dollars per unit)	$ 0.89	$ 1.18	$ 0.14
Distributions declared and paid per limited partner unit in respective periods (in dollars per unit)	$ 2.1650	$ 2.0800	$ 2.0000