Supplemental Financial Data - Oil and Gas Producing Activities (unaudited) (Details)	12 Months Ended
	Dec. 31, 2019 MBbls MMcf	Dec. 31, 2018 MBbls MMcf
Summary of proved developed and undeveloped oil and gas reserves
Proved reserves, beginning of year | MMcf	580,326	87,216
Revisions of previous estimates | MMcf	12,310	(21,868)
Extensions and discoveries | MMcf	6,605
Production | MMcf	(25,182)	(7,702)
Purchases of reserves in-place | MMcf		522,680
Sales of reserves in-place | MMcf	(9,166)
Proved reserves, end of year | MMcf	564,893	580,326
Proved developed reserves at:
End of Year | MMcf	527,555	545,272
Proved undeveloped reserves at:
End of Year | MMcf	37,338	35,054
Oil [Member]
Summary of proved developed and undeveloped oil and gas reserves
Proved reserves, beginning of year | MBbls	18,898	919
Revisions of previous estimates | MBbls	(1,362)	(2,803)
Extensions and discoveries | MBbls	826
Production | MBbls	(589)	(451)
Purchases of reserves in-place | MBbls		21,233
Sales of reserves in-place | MBbls	(31)
Proved reserves, end of year | MBbls	17,742	18,898
Proved developed reserves at:
End of Year | MBbls	12,972	14,336
Proved undeveloped reserves at:
End of Year | MBbls	4,770	4,562
Natural Gas [Member]
Summary of proved developed and undeveloped oil and gas reserves
Proved reserves, beginning of year | MMcf	455,400	81,702
Revisions of previous estimates | MMcf	24,194	1,832
Extensions and discoveries | MMcf	1,187
Production | MMcf	(21,436)	(4,798)
Purchases of reserves in-place | MMcf		376,664
Sales of reserves in-place | MMcf	(8,980)
Proved reserves, end of year | MMcf	450,365	455,400
Proved developed reserves at:
End of Year | MMcf	444,104	450,424
Proved undeveloped reserves at:
End of Year | MMcf	6,261	4,976
Natural gas liquids [Member]
Summary of proved developed and undeveloped oil and gas reserves
Proved reserves, beginning of year | MBbls	1,923
Revisions of previous estimates | MBbls	(618)	(1,147)
Extensions and discoveries | MBbls	77
Production | MBbls	(36)	(33)
Purchases of reserves in-place | MBbls		3,103
Sales of reserves in-place | MBbls
Proved reserves, end of year | MBbls	1,346	1,923
Proved developed reserves at:
End of Year | MBbls	936	1,472
Proved undeveloped reserves at:
End of Year | MBbls	410	451