Supplemental Financial Data - Oil and Gas Producing Activities (unaudited) (Details Textual) - Bcfe	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Supplemental Financial Data - Oil and Gas Producing Activities (unaudited) (Textual)
Proved reserves attributable to non-controlling interests	3.4	3.3
Discount rate, description	All cash flow amounts, including income taxes, are discounted at 10%.