Asset Retirement Obligation - Asset Retirement Obligation Summary (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013	Dec. 31, 2012
Asset Retirement Obligation Disclosure [Abstract]
Oil and gas producing properties - asset retirement obligation	$ 2	[1]	$ 2	$ 4
Estimated well life	27 years 6 months

[1] This is a recurring Level 3 fair value measurement.