Derivative Instruments/Hedging (Details 3) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Liability
Total gross amounts presented in accompanying balance sheet	$ 8,506	$ 389
Nondesignated [Member]
Asset
Total gross amounts presented in accompanying balance sheet		4,268
Less: gross amounts not offset in the accompanying balance sheet		(389)
Net amount:		3,879
Liability
Total gross amounts presented in accompanying balance sheet	8,506	389
Less: gross amounts not offset in the accompanying balance sheet		(389)
Net amount:	8,506
Nondesignated [Member] | Oil Contracts [Member] | Other Current Assets [Member]
Asset
Total gross amounts presented in accompanying balance sheet		1,805
Nondesignated [Member] | Oil Contracts [Member] | Other Current Liabilities [Member]
Liability
Total gross amounts presented in accompanying balance sheet	5,974	389
Nondesignated [Member] | Natural Gas Contracts [Member] | Other Current Assets [Member]
Asset
Total gross amounts presented in accompanying balance sheet		2,463
Nondesignated [Member] | Natural Gas Contracts [Member] | Other Current Liabilities [Member]
Liability
Total gross amounts presented in accompanying balance sheet	$ 2,532