Derivative Financial Instruments (Details 3) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Derivative instruments, Balance Sheet Location
Derivatives assets - current	$ 155,796	$ 182,640
Derivatives assets-long-term	40,675	59,856
Derivatives liabilities - current	(1,473)	(1,155)
Derivatives liabilities - long-term	(12,377)	(4,196)
Not designated as hedging instruments
Derivative instruments, Balance Sheet Location
Total	182,621	237,145
Commodity derivatives | Not designated as hedging instruments
Derivative instruments, Balance Sheet Location
Derivatives assets - current	155,796	182,640
Derivatives assets-long-term	40,675	59,197
Derivatives liabilities - current	(60)
Derivatives liabilities - long-term	(11,055)	(4,196)
Net deferred premiums payable related to commodity derivative contracts	6,300	6,200
Net deferred premiums payable related to commodity derivative contracts	8,500	6,900
Interest rate contracts | Not designated as hedging instruments
Derivative instruments, Balance Sheet Location
Derivatives assets-long-term		659
Derivatives liabilities - current	(1,413)	$ (1,155)
Derivatives liabilities - long-term	$ (1,322)