Acquisitions (Proforma Financial Results - Prize And East Texas Oil Field) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Total revenues	$ 104,886	$ 94,104
Operating income	18,934	25,656
Net income (loss)	(8,174)	(8,226)
Total revenues, Proforma		116,264
Operating income, Proforma		34,720
Net income (loss), Proforma		$ (656)
Limited Partners - Public And Affiliated Common Units [Member]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Unitholders' (basic and diluted) (in dollars per unit)	(0.33)	(0.49)
Unitholders' (basic and diluted) (in dollars per unit), Proforma		(0.22)
Limited Partners-Affiliated - Subordinated [Member]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Unitholders' (basic and diluted) (in dollars per unit)		(0.49)
Unitholders' (basic and diluted) (in dollars per unit), Proforma		(0.22)