Commitments and Contingencies (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	3 Months Ended		6 Months Ended
	Jul. 31, 2009	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011 bbl	Jun. 30, 2010
Uinta Crude Oil Sales Contract
Minimum volume of Uinta light crude oil required to be purchased under crude oil sales contract (in Bbl/D)				5,000
Gross oil production from Uinta properties (in Bbl/D)				3,500
E. Texas Gathering System
Cash proceeds from the E. Texas financing obligation	$ 18.4
Net book value of E. Texas property	16.7
E. Texas gathering system expenses incurred		$ 1.4	$ 1.5	$ 3.1	$ 2.6