Supplementory Income Statement - Supplementary Income statement (Details) - USD ($)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement Related Disclosures [Abstract]
Maintenance and repairs	$ 29,000	$ 47,000	$ 38,000
Production taxes	203,000	242,000	154,000
Taxes, other than payroll and income taxes	$ 18,000	$ 14,000	$ 11,000

The aggregate costs of keeping the property in good condition but that do not appreciably prolong the life or increase the value of the property.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.2)
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration