Acquisitions (Proforma Financial Results - Prize And East Texas Oil Field) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	0 Months Ended	12 Months Ended
	Dec. 31, 2010	Dec. 31, 2012	Dec. 31, 2011
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Unitholders' (basic) (in dollars per unit)	(0.21)	0.19	0.10
Prize And East Texas Oil Field Acquistion [Member]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Total Revenue, Proforma		$ 429,296	$ 443,948
Operating income, Proforma		96,177	125,322
Net income (loss), Proforma		$ 100,834	$ 115,842
Limited Partners-Affiliated - Common [Member]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Unitholders' (basic) (in dollars per unit)	(0.21)	0.19	0.10
Limited Partners-Affiliated - Common [Member] | Prize And East Texas Oil Field Acquistion [Member]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Unitholders' (basic) (in dollars per unit), Proforma		$ 0.63	$ 0.69
Unitholders' (diluted) (in dollars per unit), Proforma		$ 0.60	$ 0.69
Limited Partners-Affiliated - Subordinated [Member] | Prize And East Texas Oil Field Acquistion [Member]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Unitholders' (basic) (in dollars per unit), Proforma		$ 0.66	$ 0.69