Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Derivative instruments carried at fair value in Condensed Consolidated Balance Sheet
Total carrying value of derivative assets in Condensed Consolidated Balance Sheets	$ 34,940	$ 37,428
Total carrying value of derivative liabilities in Condensed Consolidated Balance Sheets	(874)
Recurring | Significant other observable inputs (Level 2) | Commodity contracts
Derivative instruments carried at fair value in Condensed Consolidated Balance Sheet
Total carrying value of derivative assets in Condensed Consolidated Balance Sheets	5,405	14,812
Total carrying value of derivative liabilities in Condensed Consolidated Balance Sheets	(95)
Recurring | Significant unobservable inputs (Level 3) | Commodity contracts
Derivative instruments carried at fair value in Condensed Consolidated Balance Sheet
Total carrying value of derivative assets in Condensed Consolidated Balance Sheets	8,480	3,840
Total carrying value of derivative liabilities in Condensed Consolidated Balance Sheets	(173)
Recurring | Significant unobservable inputs (Level 3) | Embedded derivatives in commodity contracts
Derivative instruments carried at fair value in Condensed Consolidated Balance Sheet
Total carrying value of derivative assets in Condensed Consolidated Balance Sheets	21,055	$ 18,776
Total carrying value of derivative liabilities in Condensed Consolidated Balance Sheets	$ (606)