Commitments and Contingencies (Details) (USD $)	12 Months Ended
	Dec. 31, 2012 acre		Dec. 31, 2011	Dec. 31, 2010
Leases
Operating Leases, Rent Expense	$ 1,600,000		$ 1,000,000	$ 1,000,000
Capital Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2013	1,083,000	[1]
2014	609,000	[1]
2015	209,000	[1]
Thereafter	0	[1]
Total minimum lease payments	1,901,000	[1]
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2013	3,960,000	[2]
2014	3,819,000	[2]
2015	3,843,000	[2]
Thereafter	3,865,000	[2]
Total minimum lease payments	15,487,000	[2]
Non-Cancelable Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2013	5,043,000
2014	4,428,000
2015	4,052,000
Thereafter	3,865,000
Total minimum lease payments	17,388,000
The portion of the lease in our chain	40
Lands subject to plaintiffs' claims	3
Plaintiffs contend of cost to remediate the surface	$ 8,000,000
Drilling Rigs [Member]
Non-Cancelable Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Number of drilling rigs subject to operating leases	2

[1] Relates to vehicle leases.

[2] Includes leases for two drilling rigs.