Deferred Revenue (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014 bbl	Dec. 31, 2013 bbl
Deferred Revenue Arrangement [Line Items]
Deferred revenue per agreement	$ 14,157
Three Seperate Forward Sale Agreements [Member]
Deferred Revenue Arrangement [Line Items]
Deferred revenue per agreement	$ 22,500	$ 22,500
Number of barrels of oil to be delivered	200,000	200,000