Earnings Per Common Unit (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Earnings (Loss) Per Common Unit
Net (loss) income attributable to the Partnership's unitholders	$ (101,486)	$ 8,977	$ (110,569)	$ 21,469
Less: Income allocable to phantom units	644	551	1,286	1,096
(Loss) income available for common unitholders - basic	(102,130)	8,426	(111,855)	20,373
Add: Income allocable to phantom units and DER expense		574		1,141
(Loss) income available for common unitholders - diluted	$ (102,130)	$ 9,000	$ (111,855)	$ 21,514
Weighted average common units outstanding-basic (in units)	186,855,000	164,613,000	186,771,000	161,727,000
Potential common shares (Class B and phantom units)		16,624,000		16,651,000
Weighted average common units outstanding-diluted (in units)	186,855,000	181,237,000	186,771,000	178,378,000
Net (loss) income attributable to the Partnership's common unitholders per common unit:
Basic (in dollars per unit)	$ (0.55)	$ 0.05	$ (0.60)	$ 0.13
Diluted (in dollars per unit)	$ (0.55)	$ 0.05	$ (0.60)	$ 0.12
Potential common shares excluded from calculation as anti-dilutive (in units)	12,717,000		12,726,000
Class B Units
Earnings (Loss) Per Common Unit
Net (loss) income attributable to the Partnership's unitholders	$ 0	$ 0	$ 0	$ 0
Net (loss) income attributable to the Partnership's common unitholders per common unit:
Basic (in dollars per unit)	$ 0.00	$ 0.00	$ 0.00	$ 0.00
Diluted (in dollars per unit)	$ 0.00	$ 0.00	$ 0.00	$ 0.00