Supplemental Financial Data - Oil and Gas Producing Activities (unaudited) (Details 7)	12 Months Ended
	Dec. 31, 2019 $ / Bbl $ / Mcf	Dec. 31, 2018 $ / Bbl $ / Mcf
Oil [Member]
Average Sales Price And Production Cost Per Unit [Abstract]
Price per unit used to prepare reserve estimates, based upon average prices | $ / Bbl	55.69	65.56
Natural Gas [Member]
Average Sales Price And Production Cost Per Unit [Abstract]
Price per unit used to prepare reserve estimates, based upon average prices | $ / Mcf	2.58	3.10