Supplemental Information On Oil And Gas Exploration And Production Activities (Unaudited) - Changes in Quantities of Proved Oil and natural Gas Reserves (Details)	12 Months Ended
	Dec. 31, 2018 MBoe MBbls MMcf	Dec. 31, 2017 MBoe MBbls MMcf	Dec. 31, 2016 MBoe MBbls MMcf
Reserve Quantities [Line Items]
Beginning balance | MBoe	79,976	12,051
Extensions and discoveries | MBoe	16,209	30,763
Sales of minerals in place | MBoe	(6,596)	(2,976)
Purchases of minerals in place | MBoe	6,810	45,911
Production | MBoe	(3,627)	(2,872)
Revision to previous estimates | MBoe	6,075	(2,901)
Ending Balance | MBoe	98,847	79,976
Proved developed reserves | MBoe	23,646	19,961	9,361
Proved undeveloped reserves | MBoe	75,201	60,015	2,690
Oil (MBbl)
Reserve Quantities [Line Items]
Beginning balance	47,327	7,111
Extensions and discoveries	10,148	19,558
Sales of minerals in place	(2,651)	(1,833)
Purchases of minerals in place	3,532	28,176
Production	(2,370)	(1,828)
Revision to previous estimates	3,048	(3,857)
Ending balance	59,034	47,327
Proved developed reserves	14,325	11,949	6,052
Proved undeveloped reserves	44,709	35,378	1,059
Natural Gas (MMcf)
Reserve Quantities [Line Items]
Beginning balance | MMcf	91,088	20,401
Extensions and discoveries | MMcf	17,673	29,644
Sales of minerals in place | MMcf	(14,300)	(6,853)
Purchases of minerals in place | MMcf	9,890	46,709
Production | MMcf	(3,610)	(3,260)
Revision to previous estimates | MMcf	12,476	4,447
Ending Balance | MMcf	113,217	91,088
Proved developed reserves | MMcf	26,110	23,336	13,545
Proved undeveloped reserves | MMcf	87,107	67,752	6,856
NGLs (MBbl)
Reserve Quantities [Line Items]
Beginning balance	17,468	1,540
Extensions and discoveries	3,116	6,264
Sales of minerals in place	(1,562)	(1)
Purchases of minerals in place	1,629	9,950
Production	(655)	(500)
Revision to previous estimates	947	215
Ending balance	20,943	17,468
Proved developed reserves	4,969	4,123	1,051
Proved undeveloped reserves	15,974	13,345	489