Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013
Cash flows from operating activities:
Net income	$ 37,170	[1]	$ 33,943	[1]
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	93,203		85,496
Accretion of asset retirement obligations	6,534		5,411
Recognition of unit-based awards	5,815		5,120
Loss (gain) on derivative contracts, net	20,191		14,414
Cash received (paid) on settlement of derivative contracts	1,177		13,093
Gain on deferred Class B unit obligation	(6,883)
Other items	6,069		3,445
Changes in operating assets and liabilities:
Accounts receivable and other assets	(16,134)		(20,716)
Accounts payable and other liabilities	(12,678)		1,612
Net cash provided by operating activities	134,464		141,818
Cash flows from investing activities:
Additions to oil and natural gas properties	(119,437)		(65,898)
Acquisitions	(44,251)		(101,696)
Divestitures of oil and gas properties	1,300
Proceeds from sale of available-for-sale securities	3,749		4,643
Purchases of available-for-sale securities	(4,022)		(4,268)
Net cash used in investing activities	(162,661)		(167,219)
Cash flows from financing activities:
Proceeds from issuance of units			87
Management incentive fee to the general partner	(1,399)		(2,014)
Distributions to unitholders	(106,582)		(106,226)
Units withheld for employee payroll tax obligation	(1,023)
Proceeds from bank borrowings	178,000		150,000
Repayments on bank borrowings	(38,000)		(20,000)
Deferred financing costs			(1,828)
Other			(390)
Net cash (used in) provided by financing activities	30,996		19,629
Increase (decrease) in cash	2,799		(5,772)
Cash and cash equivalents at beginning of period	13,360		31,836
Cash and cash equivalents at ending of period	$ 16,159		$ 26,064

[1] Includes net income attributable to noncontrolling interest