Tax effects of temporary differences representing the net DTA (DTL) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
DTA, Federal net operating losses (NOLs)	$ 71,736	$ 58,438
DTA, Alternative minimum tax credits	0	138
DTA, Other loss carryforwards	583	619
DTA, Asset retirement obligations	920	2,329
Deferred Tax Assets, Hedging Transactions	0	29
DTA, Unrealized share-based compensation	906	872
DTA, Other	956	2,190
DTA, Valuation Allowance	(42,335)	(58,398)
Total deferred tax assets	32,766	6,217
Deferred tax liabilities:
DTL, Oil and gas exploration and development costs	(30,935)	(6,054)
Deferred Tax Liabilities, Derivatives	(2,817)	0
DTL, Other	(28)	(163)
Total deferred tax liabilites	33,780	6,217
Net deferred tax liabilities	$ (1,014)	$ 0