Consolidated Statements Of Operations (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
Revenues:
Oil and natural gas sales	$ 104,638		$ 88,441		$ 208,806		$ 181,600
Processing and other	792		915		1,510		1,860
Total revenues	105,430		89,356		210,316		183,460
Operating Expenses:
Production expenses	42,489		36,144		85,237		68,911
Depreciation, depletion and amortization	26,663		25,326		57,478		49,610
Accretion of asset retirement obligations	1,758		1,375		3,490		2,697
General and administrative	10,098		10,182		20,194		20,169
Acquisition and transaction costs	59		920		620		1,008
Total operating expenses	81,067		73,947		167,019		142,395
Operating income	24,363		15,409		43,297		41,065
Other income (expense):
Gain (losses) on commodity derivative contracts	50,329		121,568		34,205		94,544
Interest expense, net	(10,270)		(10,576)		(21,323)		(19,354)
Total other income (expense), net	39,253		116,021		12,194		82,108
Income before income taxes	63,616		131,430		55,491		123,173
Income tax expense, net	(2)		(730)		(51)		(699)
Net income	63,614		130,700		55,440		122,474
Realized Gain (Loss) [Member]
Other income (expense):
Gain (losses) on commodity derivative contracts	6,233		11,896		14,398		17,664
Commodity Contract [Member]
Other income (expense):
Gain (losses) on commodity derivative contracts	49,523	[1]	126,597	[1]	33,517	[1]	101,462	[1]
Commodity Contract [Member] | Realized Gain (Loss) [Member]
Other income (expense):
Gain (losses) on commodity derivative contracts	7,435	[1]	14,222	[1]	16,745	[1]	22,293	[1]
Commodity Contract [Member] | Unrealized Gain (Loss) [Member]
Other income (expense):
Gain (losses) on commodity derivative contracts	$ 42,088		$ 112,375		$ 16,772		$ 79,169
Limited Partners - Public And Affiliated Common Units [Member]
Net income per limited partner unit:
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
Weighted average number of limited partner units outstanding:
Common units (basic) (in units)	59,556	[2]	36,114	[2]	58,455	[2]	32,486	[2]
Common units (diluted) (in units)	82,356	[2]	52,780	[2]	58,455	[2]	49,153	[2]
Limited Partners-Affiliated - Subordinated [Member]
Net income per limited partner unit:
Unitholders' (basic) (in dollars per unit)			$ 2.12				$ 1.76
Unitholders' (diluted) (in dollars per unit)			$ 1.65	[2]			$ 1.50	[2]
Weighted average number of limited partner units outstanding:
Subordinated units (basic and diluted) (in units)			7,146	[2]			7,146	[2]

[1] Gain (loss) on commodity derivative contracts is located in other income (expense) in the consolidated statements of operations.

[2] 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.