Supplemental Oil and Gas Disclosures (Unaudited) (Details 3) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Discounted Future Net Cash Flows Detail [Table]
Future cash inflows	$ 28,873	$ 673,295
Future costs
Production	10,240	199,196
Development and abandonment	7,922	264,074
Future net cash flows before income taxes	10,711	210,025
Future income taxes	(1,513)	(53,481)
Future net cash flows	9,198	156,544
Discount at 10% annual rate	(2,723)	(23,275)
Standardized measure of discounted future net cash flows	6,475	133,269
Changes in Discounted Future Net Cash Flows Detail [Table]
Standardized measure, beginning of year	133,269	86,049	60,348
Sales, net of production costs	(48,445)	(74,718)	(95,076)
Net change in prices, net of production costs	(11,916)	92,065	43,098
Changes in future development and abandonment costs	43,792	(48,002)	2,235
Development and abandonment costs incurred	25,083	42,151	10,585
Accretion of discount	17,909	9,720	6,396
Net change in income taxes	44,612	(34,665)	(7,536)
Purchases of reserves in place	0	8,694	0
Extensions and discoveries	0	63,411	27,873
Sales of reserves in place	(198,324)	(58)	1,268
Net change due to revision in quantity estimates	(10,814)	(13,738)	41,045
Changes in production rates (timing) and other	11,309	2,360	(4,187)
Subtotal	(126,794)	47,220	25,701
Standardized measure, end of year	$ 6,475	$ 133,269	$ 86,049