Consolidated Statements Of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Cash flows from operating activities:
Net income	$ 46,883	$ 87,604
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	61,428	58,295
Accretion of asset retirement obligations	2,645	2,033
Recognition of unit-based awards	2,124	990
General and administrative expense contributed by affiliates	22,224	21,252
Unrealized gains on derivative contracts	(23,011)	(135,590)
Deferred income tax benefit	372	361
Other items	3,222	1,950
Changes in operating assets and liabilities:
Accounts receivable and other assets	(11,232)	(16,529)
Accounts payable and other liabilities	5,731	2,015
Net cash provided by operating activities	110,386	22,381
Cash flows from investing activities:
Additions to oil and gas properties	(80,566)	(43,917)
Proceeds from the sale of oil and gas properties	3,082	1,327
Acquisitions	(225,118)
Net cash used in investing activities	(302,602)	(42,590)
Cash flows from financing activities:
Proceeds from unit offering, net of offering costs	161,958	41,963
Proceeds from senior note offering, net of discount	295,860
Distributions to the Fund		(42,000)
Proceeds from issuance of units to the General Partner	115	715
Management incentive fee to the General Partner	(3,155)
Distributions to unitholders	(70,959)	(31,223)
Contributions from the Predecessor		8,985
Proceeds from bank borrowings	116,500	41,000
Repayments on bank borrowings	(291,500)
Deferred financing costs	(8,892)	(214)
Net cash provided by financing activities	199,927	19,226
Increase (decrease) in cash	7,711	(983)
Cash at beginning of period	17,433	2,195
Cash at end of period	$ 25,144	$ 1,212