Subsidiary Guarantors (Condensed Consolidated Statements Of Cash Flows) (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Cash flows from operating activities:
Net cash (used in) provided by operating activities	$ 141,818	$ 157,957
Cash flows from investing activities:
Additions to oil and gas properties	(65,898)	(100,940)
Acquistions, net of cash acquired	(101,696)	(225,118)
Proceeds from sale of available-for-sale securities	4,643
Purchases of available-for-sale securities	(4,268)
Net cash (used in) provided by investing activities	(167,219)	(322,976)
Cash flows from financing activities:
Distributions to unitholders	(106,226)	(70,959)
Proceeds from bank borrowings	150,000	116,500
Repayments on bank borrowings	(20,000)	(291,500)
Other	(4,145)
Net cash provided by (used in) financing activities	19,629	172,730
Increase (decrease) in cash	(5,772)	7,711
Cash and Cash Equivalents, at Carrying Value, Beginning Balance	31,836	17,433
Cash and Cash Equivalents, at Carrying Value, Ending Balance	26,064	25,144
Parent Co - Issuer [Member]
Cash flows from operating activities:
Net cash (used in) provided by operating activities	(28,050)
Cash flows from investing activities:
Distributions from subsidiaries	136,449
Net cash (used in) provided by investing activities	136,449
Cash flows from financing activities:
Distributions to unitholders	(106,226)
Other	(2,241)
Net cash provided by (used in) financing activities	(108,467)
Increase (decrease) in cash	(68)
Cash and Cash Equivalents, at Carrying Value, Beginning Balance	68
Guarantor [Member]
Cash flows from operating activities:
Net cash (used in) provided by operating activities	169,511
Cash flows from investing activities:
Additions to oil and gas properties	(65,898)
Acquistions, net of cash acquired	(105,177)
Net cash (used in) provided by investing activities	(171,075)
Cash flows from financing activities:
Proceeds from bank borrowings	150,000
Repayments on bank borrowings	(20,000)
Repayments on intercompany borrowings	(33,213)
Distributions to Parent	(103,236)
Other	(1,904)
Net cash provided by (used in) financing activities	(8,353)
Increase (decrease) in cash	(9,917)
Cash and Cash Equivalents, at Carrying Value, Beginning Balance	31,768
Cash and Cash Equivalents, at Carrying Value, Ending Balance	21,851
Non-Guarantor [Member]
Cash flows from operating activities:
Net cash (used in) provided by operating activities	357
Cash flows from investing activities:
Acquistions, net of cash acquired	3,481
Proceeds from sale of available-for-sale securities	4,643
Purchases of available-for-sale securities	(4,268)
Net cash (used in) provided by investing activities	3,856
Cash flows from financing activities:
Increase (decrease) in cash	4,213
Cash and Cash Equivalents, at Carrying Value, Ending Balance	4,213
Eliminations [Member]
Cash flows from investing activities:
Distributions from subsidiaries	(136,449)
Net cash (used in) provided by investing activities	(136,449)
Cash flows from financing activities:
Repayments on intercompany borrowings	33,213
Distributions to Parent	103,236
Net cash provided by (used in) financing activities	$ 136,449