Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash flows from operating activities:
Net income	$ 17,170	$ 13,570
Adjustments to reconcile net income to net cash provided by operating activities:
Depletion, depreciation and amortization	6,884	4,832
Deferred income taxes	163	43
Accretion of discount on asset retirement obligations	207	188
Amortization of debt related costs	64	45
Amortization of unit-based compensation	232	170
Commodity derivative related activity	(584)	8,465
Other noncash expense	0	433
Change in operating assets and liabilities:
Accounts receivable	(3,681)	(984)
Inventories	202	(35)
Prepaid expenses	53	25
Accounts payable	1,878	2,042
Interest payable	159	117
Income taxes payable to affiliate	57	136
Asset retirement obligations	(356)	(447)
Other current liabilities	(64)	0
Net cash provided by operating activities	22,384	28,600
Cash flows from investing activities:
Additions to oil and gas properties	(32,790)	(23,308)
Net cash used in investing activities	(32,790)	(23,308)
Cash flows from financing activities:
Borrowings under credit facility	28,000	67,000
Principal payments on credit facility	0	(49,000)
Payment of financing fees	0	(1,261)
Distributions to unitholders	(18,590)	(18,232)
Net cash provided by (used in) financing activities	9,410	(1,493)
Net increase (decrease) in cash	(996)	3,799
Cash, beginning of period	1,601	1,176
Cash, end of period	$ 605	$ 4,975