NET INCOME PER LIMITED PARTNER UNIT (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Earnings Per Share Disclosure [Line Items]
Net (loss) income	$ (46,581)	$ 28,593
Net loss (income) attributable to participating securities	(498)
Limited partners' interest in net income	(46,147)	28,021
Percentage of general partnership interest	2.00%
Weighted average limited partner units outstanding:
Denominator for basic net income (loss) per limited partner unit	42,556,000	40,440,000
Dilutive phantom units		320,000	[1]
Total	42,556,000	40,760,000
Net income per limited partner unit:
Basic	(1.08)	0.69
Diluted	(1.08)	0.69
Equity awards not included in computation of diluted net income (loss) per limited partner unit	600,000
General Partner Interests
Earnings Per Share Disclosure [Line Items]
Net income available for general partners	932	(572)
Common units
Weighted average limited partner units outstanding:
Denominator for basic net income (loss) per limited partner unit	42,556,000	36,425,000
Class B Unitholders [Member]
Earnings Per Share Disclosure [Line Items]
Net (loss) income		$ 2,688
Weighted average limited partner units outstanding:
Denominator for basic net income (loss) per limited partner unit		3,873,000
Performance Units [Member]
Weighted average limited partner units outstanding:
Denominator for basic net income (loss) per limited partner unit		142,000

[1] Phantom units totaling 0.6 million units were not included in the computation of diluted net (loss) income per limited partner unit for the three months ended Marc