Acquisitions (Proforma Financial Results - Prize And East Texas Oil Field) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012		Jun. 30, 2013	Jun. 30, 2012
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Total revenues	$ 105,430	$ 89,356		$ 210,316	$ 183,460
Operating income	24,363	15,409		43,297	41,065
Net income	63,614	130,700		55,440	122,474
Prize And 2012 East Texas Oil Field Acquistion [Member]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Total revenues	105,430			210,316
Operating income	24,363			43,297
Net income	63,614			55,440
Total revenues, Proforma		103,498			219,761
Operating income, Proforma		21,162			56,153
Net income (loss), Proforma		$ 135,216			$ 134,832
Limited Partners - Public And Affiliated Common Units [Member]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Unitholders' (basic) (in dollars per unit)	$ 0.89	$ 2.15		$ 0.58	$ 1.92
Unitholders' (diluted) (in dollars per unit)	$ 0.77	$ 1.67		$ 0.58	$ 1.60
Limited Partners - Public And Affiliated Common Units [Member] | Prize And 2012 East Texas Oil Field Acquistion [Member]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Unitholders' (basic) (in dollars per unit)	$ 0.89			$ 0.58
Unitholders' (diluted) (in dollars per unit)	$ 0.77			$ 0.58
Unitholders' (basic) (in dollars per unit), Proforma		$ 2.17			$ 1.95
Unitholders' (diluted) (in dollars per unit), Proforma		$ 1.70			$ 1.66
Limited Partners-Affiliated - Subordinated [Member]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Unitholders' (basic) (in dollars per unit)		$ 2.12			$ 1.76
Unitholders' (diluted) (in dollars per unit)		$ 1.65	[1]		$ 1.50	[1]
Limited Partners-Affiliated - Subordinated [Member] | Prize And 2012 East Texas Oil Field Acquistion [Member]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Unitholders' (basic) (in dollars per unit), Proforma		$ 2.16			$ 1.95
Unitholders' (diluted) (in dollars per unit), Proforma		$ 1.69			$ 1.65

[1] For the three and six months ended June 30, 2013 and 2012, we had weighted average preferred units outstanding of 16,666,667. For the three months ended June 30, 2013 and 2012, we had 6,133,558 and zero Class B units outstanding, respectively. For the six months ended June 30, 2013 and 2012, we had 4,961,597 and zero Class B units outstanding, respectively. The preferred and Class B units are contingently convertible into common units and could potentially dilute earnings per unit in the future.