Derivative Financial Instruments - Derivatives (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Derivative instruments, Balance Sheet Location
Derivatives assets - current	$ 34,899,000	$ 31,698,000
Derivatives assets-long-term	8,031,000	3,808,000
Derivatives liabilities - current	(8,916,000)	(19,692,000)
Derivatives liabilities - long-term	(5,299,000)	(14,123,000)
Not designated as hedging instruments
Derivative instruments, Balance Sheet Location
Total	28,715,000	1,691,000
Commodity derivatives | Not designated as hedging instruments
Derivative instruments, Balance Sheet Location
Derivatives assets - current	34,899,000	31,698,000
Derivatives assets-long-term	7,390,000	3,226,000
Derivatives liabilities - current	(8,883,000)	(19,163,000)
Derivatives liabilities - long-term	(5,299,000)	(14,123,000)
Net deferred premiums receivable related to commodity derivative contracts - non current liabilities	400,000
Net deferred premiums payable related to commodity derivative contracts - current assets	3,500,000	3,900,000
Net deferred premiums payable related to commodity derivative contracts - non current assets	3,700,000	2,500,000
Net deferred premiums payable related to commodity derivative contracts - current liabilities	5,500,000	6,200,000
Net deferred premiums payable related to commodity derivative contracts - non current liabilities		600,000
Commodity derivatives | Not designated as hedging instruments | Oil and gas revenue
Derivative instruments, Balance Sheet Location
Derivatives liabilities - current	0	(30,900)
Interest rate contracts | Not designated as hedging instruments
Derivative instruments, Balance Sheet Location
Derivatives assets-long-term	641,000	582,000
Derivatives liabilities - current	$ (33,000)	$ (529,000)