Condensed Consolidated Statements of Changes in Owners' Equity (USD $) In Thousands	Common Unitholders [Member]	Class B Unitholders [Member]	General Partner [Member]	Total
Beginning Balance at Dec. 31, 2011	$ 935,425	$ 232	$ (15,618)	$ 920,039
Conversion vested phantom units	2,836			2,836
Proceeds from public equity offering, net of offering costs of $304	262,529			262,529
Contributions from general partner			5,714	5,714
Distributions	(85,050)	(8,878)	(1,917)	(95,845)
Equity-based compensation	10,374			10,374
Net loss	(5,873)	(468)	(129)	(6,470)
Ending Balance at Sep. 30, 2012	1,120,241	(9,114)	(11,950)	1,099,177
Beginning Balance at Dec. 31, 2012	1,072,175		(12,351)	1,059,824
Conversion vested phantom units	2,365			2,365
Contributions from general partner			334	334
Distributions	(99,643)		(2,003)	(101,646)
Equity-based compensation	12,640		258	12,898
Net loss	(25,520)		(521)	(26,041)
Ending Balance at Sep. 30, 2013	$ 962,017		$ (14,283)	$ 947,734