Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data	Jun. 30, 2011	Dec. 31, 2010
Oil and natural gas properties, accumulated depreciation, depletion and amortization	$ 210,073	$ 176,897
Other property, accumulated depreciation and amortization	$ 536	$ 465
Common unitholders, units issued	34,173,650	30,510,313
Common unitholders, units outstanding	34,173,650	30,510,313