Income Taxes (Details Textuals) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Valuation Allowance [Line Items]
Loss carryforwards - state	$ 42,625	$ 37,175
Loss carryforwards - federal	27,078	52,580
Enhanced oil recovery credit carryforwards	51,100
Research and development credits	21,600
Tax credit carryover	41,132	34,837
Tax valuation allowance on state NOLs	2,900	$ 33,600
Unrecognized Tax Benefits	5,400
State of Louisiana [Member]
Valuation Allowance [Line Items]
Loss carryforwards - state	$ 36,500