Supplemental Financial Data - Oil and Gas Producing Activities (unaudited) (Details)	12 Months Ended
	Dec. 31, 2018 MMcf MMBbls	Dec. 31, 2018 MMcf MBbls MMBbls	Dec. 31, 2018 MMcf MMBbls	Dec. 31, 2017 MMcf MMBbls	Dec. 31, 2017 MMcf MBbls MMBbls	Dec. 31, 2017 MMcf MMBbls
Summary of Proved undeveloped and developed oil and gas reserves expected to be recovered from new wells
Proved reserves, beginning of year	87,216			79,557
Revisions of previous estimates	(21,868)			12,841
Extensions and discoveries				232
Production	(7,702)			(5,414)
Purchases of reserves in-place	522,680
Sales of reserves in-place
Proved reserves, end of year	580,326			87,216
Proved developed reserves at:
End of Year	545,272	545,272	545,272	87,216	87,216	87,216
Proved undeveloped reserves at:
End of Year	35,054	35,054	35,054	96	96	96
Carbon California [Member]
Summary of Proved undeveloped and developed oil and gas reserves expected to be recovered from new wells
Proved reserves, beginning of year	14,124
Proved reserves, end of year				14,124
Carbon Appalchia [Member]
Summary of Proved undeveloped and developed oil and gas reserves expected to be recovered from new wells
Proved reserves, beginning of year	100,507
Proved reserves, end of year				100,507
Company [Member]
Summary of Proved undeveloped and developed oil and gas reserves expected to be recovered from new wells
Proved reserves, beginning of year	79,557			79,557
Proved reserves, end of year	87,216			79,557
Oil [Member]
Summary of Proved undeveloped and developed oil and gas reserves expected to be recovered from new wells
Proved reserves, beginning of year		4,169	919		882	882
Revisions of previous estimates | MMBbls			(2,803)			107
Extensions and discoveries | MMBbls						16
Production | MMBbls			(451)			(86)
Purchases of reserves in-place | MMBbls			21,233
Sales of reserves in-place | MMBbls
Proved reserves, end of year			18,898		4,169	919
Proved developed reserves at:
End of Year | MMBbls	14,336	14,336	14,336	903	903	903
Proved undeveloped reserves at:
End of Year | MMBbls	4,562	4,562	4,562	16	16	16
Oil [Member] | Carbon California [Member]
Summary of Proved undeveloped and developed oil and gas reserves expected to be recovered from new wells
Proved reserves, beginning of year | MBbls		1,625
Proved reserves, end of year | MBbls					1,625
Oil [Member] | Carbon Appalchia [Member]
Summary of Proved undeveloped and developed oil and gas reserves expected to be recovered from new wells
Proved reserves, beginning of year | MBbls		72
Proved reserves, end of year | MBbls					72
Oil [Member] | Company [Member]
Summary of Proved undeveloped and developed oil and gas reserves expected to be recovered from new wells
Proved reserves, beginning of year | MBbls		882			882
Proved reserves, end of year | MBbls		919			882
Natural Gas [Member]
Summary of Proved undeveloped and developed oil and gas reserves expected to be recovered from new wells
Proved reserves, beginning of year	81,702			74,265
Revisions of previous estimates	1,832			12,199
Extensions and discoveries				136
Production	(4,798)			(4,898)
Purchases of reserves in-place	376,664
Sales of reserves in-place
Proved reserves, end of year	455,400			81,702
Proved developed reserves at:
End of Year	450,424	450,424	450,424	81,702	81,702	81,702
Proved undeveloped reserves at:
End of Year	4,976	4,976	4,976
Natural Gas [Member] | Carbon California [Member]
Summary of Proved undeveloped and developed oil and gas reserves expected to be recovered from new wells
Proved reserves, beginning of year	3,012
Proved reserves, end of year				3,012
Natural Gas [Member] | Carbon Appalchia [Member]
Summary of Proved undeveloped and developed oil and gas reserves expected to be recovered from new wells
Proved reserves, beginning of year	90,757
Proved reserves, end of year				90,757
Natural Gas [Member] | Company [Member]
Summary of Proved undeveloped and developed oil and gas reserves expected to be recovered from new wells
Proved reserves, beginning of year	74,265			74,265
Proved reserves, end of year	81,702			74,265
NGL [Member]
Summary of Proved undeveloped and developed oil and gas reserves expected to be recovered from new wells
Proved reserves, beginning of year		227
Revisions of previous estimates | MMBbls			(1,147)
Extensions and discoveries | MMBbls
Production | MMBbls			(33)
Purchases of reserves in-place | MMBbls			3,103
Sales of reserves in-place | MMBbls
Proved reserves, end of year			1,923		227
Proved developed reserves at:
End of Year | MMBbls	1,472	1,472	1,472
Proved undeveloped reserves at:
End of Year | MMBbls	451	451	451
NGL [Member] | Carbon California [Member]
Summary of Proved undeveloped and developed oil and gas reserves expected to be recovered from new wells
Proved reserves, beginning of year | MBbls		227
Proved reserves, end of year | MBbls					227