Operating Segments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Operating segment data
Revenues	$ 13,938	$ 25,524	$ 31,687	$ 50,290
Operating Income (loss)	(5,573)	8,361	(7,111)	22,064
Identifiable assets, Total	267,663		267,663		306,711
Production [Member]
Operating segment data
Revenues	11,124	23,058	25,445	44,651
Operating Income (loss)	(6,781)	8,129	(10,019)	21,259
Identifiable assets, Total	207,588		207,588		245,093
Pipeline [Member]
Operating segment data
Revenues	2,814	2,466	6,242	5,639
Operating Income (loss)	1,208	232	2,908	805
Identifiable assets, Total	$ 60,075		$ 60,075		$ 61,618