Unproved Oil and Gas Properties, Full Cost Method (Details Textual) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Unproved Oil and Gas Properties, Full Cost Method (Textual)
Inclusive of non-cash amounts	$ 174	$ 3,872
Unproved oil and gas properties unpaid amount	$ 136		$ 2,946