Property and Equipment (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Impairment of Oil and Gas Properties	$ 8,883	$ 32,466	$ 26,142
Parent Company [Member]
Impairment of Oil and Gas Properties	$ 8,883	$ 32,532	$ 25,478