Additional Operations and Balance Sheet Information - Significant purchasers / operators (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Sunoco Partners Marketing [Member]
Product Information [Line Items]
Significant Purchaser	21.00%	18.00%	18.00%
Targa Midstream Services, LLC [Member]
Product Information [Line Items]
Significant Purchaser	8.00%	9.00%	13.00%
Bedrock Producation LLC [Member]
Product Information [Line Items]
Significant Purchaser	8.00%	0.00%	0.00%
Enlink Gas Marketing, LTD [Member]
Product Information [Line Items]
Significant Purchaser	8.00%	10.00%	13.00%
ETX Energy, LLC formerly New Gulf Resources [Member]
Product Information [Line Items]
Significant Purchaser	6.00%	5.00%	7.00%
Eastex Crude Company [Member]
Product Information [Line Items]
Significant Purchaser	5.00%	3.00%	7.00%
Barnett Gathering.L.P.[Member]
Product Information [Line Items]
Significant Purchaser	5.00%	4.00%	1.00%
Ace Gathering, Inc.[Member]
Product Information [Line Items]
Significant Purchaser	4.00%	4.00%	2.00%
Peveler Pipeline ,LP [Member]
Product Information [Line Items]
Significant Purchaser	3.00%	0.00%	0.00%
Shell Trading (US) Company[Member]
Product Information [Line Items]
Significant Purchaser	3.00%	4.00%	4.00%
Pruet Production Co.[Member]
Product Information [Line Items]
Significant Purchaser	3.00%	3.00%	3.00%
Phillps 66 [Member]
Product Information [Line Items]
Significant Purchaser	3.00%	1.00%	1.00%
Hunt Crude Oil Supply[Member]
Product Information [Line Items]
Significant Purchaser	3.00%	0.00%	0.00%
ETC Texas Pipeline, Ltd [Member]
Product Information [Line Items]
Significant Purchaser	2.00%	4.00%	2.00%
Midcoast Energy Partners LP[Member]
Product Information [Line Items]
Significant Purchaser	2.00%	3.00%	4.00%
Land and Natural Resources DevelopmentMember]
Product Information [Line Items]
Significant Purchaser	1.00%	2.00%	0.00%
Enlink Crude Purchasing, LLC [Member]
Product Information [Line Items]
Significant Purchaser	1.00%	0.00%	0.00%
FDL Operating LLC [Member]
Product Information [Line Items]
Significant Purchaser	1.00%	1.00%	0.00%
Valero Energy Corporation [Member]
Product Information [Line Items]
Significant Purchaser	1.00%	1.00%	3.00%
Empire Pipeline Corp..[Member]
Product Information [Line Items]
Significant Purchaser	1.00%	1.00%	1.00%
DCP Midstream, LP [Member]
Product Information [Line Items]
Significant Purchaser	1.00%	4.00%	3.00%
XTO Energy, Inc.[Member]
Product Information [Line Items]
Significant Purchaser	1.00%	1.00%	1.00%
OXY USA, Inc. [Member]
Product Information [Line Items]
Significant Purchaser	1.00%	1.00%	2.00%
Range Resources Corporation[Member]
Product Information [Line Items]
Significant Purchaser	1.00%	1.00%	1.00%
Sandridge Energy, Inc.[Member]
Product Information [Line Items]
Significant Purchaser	1.00%	1.00%	1.00%
White Knight Production, LLC[Member]
Product Information [Line Items]
Significant Purchaser	1.00%	0.00%	0.00%
Webb Energy Resources, Inc.[Member]
Product Information [Line Items]
Significant Purchaser	0.00%	1.00%	1.00%
Enervest Operating, LLC [Member]
Product Information [Line Items]
Significant Purchaser	0.00%	10.00%	3.00%
Courson Oil & Gas, Inc.[Member]
Product Information [Line Items]
Significant Purchaser	0.00%	0.00%	1.00%
LPC Crude Oil Marketing LLC [Member]
Product Information [Line Items]
Significant Purchaser	0.00%	2.00%	3.00%
Lucid Energy Group II[Member]
Product Information [Line Items]
Significant Purchaser	0.00%	1.00%	2.00%
Enterprise Crude Oil, LLC[Member]
Product Information [Line Items]
Significant Purchaser	0.00%	1.00%	0.00%
Ward Petroleum Corporation[Member]
Product Information [Line Items]
Significant Purchaser	0.00%	0.00%	1.00%