Derivative Financial Instruments - Derivatives (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Derivative instruments, Balance Sheet Location
Derivatives assets - current	$ 31,698,000	$ 182,640,000
Derivatives assets-long-term	3,808,000	59,856,000
Derivatives liabilities - current	(19,692,000)	(1,155,000)
Derivatives liabilities - long-term	(14,123,000)	(4,196,000)
Not designated as hedging instruments
Derivative instruments, Balance Sheet Location
Total	1,691,000	237,145,000
Commodity derivatives | Not designated as hedging instruments
Derivative instruments, Balance Sheet Location
Derivatives assets - current	31,698,000	182,640,000
Derivatives assets-long-term	3,226,000	59,197,000
Derivatives liabilities - current	(19,163,000)
Derivatives liabilities - long-term	(14,123,000)	(4,196,000)
Net deferred premiums payable related to commodity derivative contracts - current assets	3,900,000	6,200,000
Net deferred premiums payable related to commodity derivative contracts - non current assets	2,500,000	6,900,000
Net deferred premiums payable related to commodity derivative contracts - current liabilities	6,200,000	0
Net deferred premiums payable related to commodity derivative contracts - non current liabilities	600,000	0
Commodity derivatives | Not designated as hedging instruments | Oil and gas revenue
Derivative instruments, Balance Sheet Location
Derivatives liabilities - current	(30,900)	0
Interest rate contracts | Not designated as hedging instruments
Derivative instruments, Balance Sheet Location
Derivatives assets-long-term	582,000	659,000
Derivatives liabilities - current	$ (529,000)	$ (1,155,000)