Note 16 - Supplemental Oil and Gas Disclosures (Unaudited) (Details Textual) Boe in Thousands	12 Months Ended
	Dec. 31, 2018 Boe	Dec. 31, 2017 Boe	Dec. 31, 2016 Boe
Proved Developed and Undeveloped Reserves Sales of Minerals in Place, Energy		1,312	1,232
Proved Developed and Undeveloped Reserves Production, Energy	3,580	2,698	2,262
Proved Developed and Undeveloped Reserve, Purchase of Mineral in Place (Energy)		189
Ira Area [Member]
Proved Developed and Undeveloped Reserves Sales of Minerals in Place, Energy	203
Delaware Locations in Ward County, TX [Member]
Number of Producing Locations Sold	1
Number of Undeveloped Locations Sold	2
Ward County, TX [Member]
Proved Developed and Undeveloped Reserves Sales of Minerals in Place, Energy	3,558
Other Miscellaneous Asset [Member]
Proved Developed and Undeveloped Reserves Sales of Minerals in Place, Energy	68
Change in Projections [Member]
Proved Developed and Undeveloped Reserves Revisions of Previous Estimates, Energy	(45)	621
Conversion of Probable Undeveloped Locations to Proved Producing Reserves [Member]
Proved Developed and Undeveloped Reserves Extensions Discoveries and Additions, Location		3
Proved Developed and Undeveloped Reserves Extensions Discoveries and Additions, Energy		2,028
Conversion of Probable Undeveloped Locations to Proved Producing Reserves [Member] | Three Fork 2nd bench Locations [Member]
Proved Developed and Undeveloped Reserves Revisions of Previous Estimates, Energy	6,525
Proved Developed and Undeveloped Reserves Revisions of Previous Estimates, Location	13
Addition of Proved Undeveloped Operated Locations [Member]
Proved Developed and Undeveloped Reserves Extensions Discoveries and Additions, Location	19
Proved Developed and Undeveloped Reserves Extensions Discoveries and Additions, Energy	8,130
Addition of Proved Undeveloped Non-operated Locations [Member]
Proved Developed and Undeveloped Reserves Extensions Discoveries and Additions, Location	2
Proved Developed and Undeveloped Reserves Extensions Discoveries and Additions, Energy	838
Conversion of Probable Undeveloped Locations to Producing Reserves [Member]
Proved Developed and Undeveloped Reserves Extensions Discoveries and Additions, Location	2
Proved Developed and Undeveloped Reserves Extensions Discoveries and Additions, Energy	1,523
Conversion of Probable Undeveloped Locations to Proved Undeveloped Reserves [Member]
Proved Developed and Undeveloped Reserves Extensions Discoveries and Additions, Location	5
Proved Developed and Undeveloped Reserves Extensions Discoveries and Additions, Energy	2,670
Conversion of Probable Undeveloped Locations to Proved Undeveloped Reserves [Member] | Ward County, TX [Member]
Proved Developed and Undeveloped Reserves Extensions Discoveries and Additions, Location		10
Proved Developed and Undeveloped Reserves Extensions Discoveries and Additions, Energy		4,343
Unit Line Well Configurations [Member]
Proved Developed and Undeveloped Reserves Extensions Discoveries and Additions, Location	3
Proved Developed and Undeveloped Reserves Extensions Discoveries and Additions, Energy	1,692
Non-operated Proved Non-producintg Locations [Member]
Proved Developed and Undeveloped Reserves Extensions Discoveries and Additions, Location	6
Proved Developed and Undeveloped Reserves Extensions Discoveries and Additions, Energy	126
Minerals Purchased in Place [Member]
Proved Developed and Undeveloped Reserves Extensions Discoveries and Additions, Energy	877
Increase in Projections [Member] | Ward County, TX [Member]
Proved Developed and Undeveloped Reserves Revisions of Previous Estimates, Energy		1,951
Increase in Economic Life Expectations [Member] | Ward County, TX [Member]
Proved Developed and Undeveloped Reserves Revisions of Previous Estimates, Energy		523
Proved Developed and Undeveloped Reserves Revisions of Previous Estimates, Location		7
Proved Developed and Undeveloped Reserves Production, Energy		2,698
Addition of New Producing Wells [Member] | Ward County, TX [Member]
Proved Developed and Undeveloped Reserves Extensions Discoveries and Additions, Location		3
Proved Developed and Undeveloped Reserves Extensions Discoveries and Additions, Energy		1,229	449
Addition of New Producing Wells [Member] | Atascosa County, TX [Member]
Proved Developed and Undeveloped Reserves Extensions Discoveries and Additions, Energy		240
Addition of Proved Undeveloped Locations [Member] | Ward County, TX [Member]
Proved Developed and Undeveloped Reserves Extensions Discoveries and Additions, Location			5
Proved Developed and Undeveloped Reserves Extensions Discoveries and Additions, Energy		11,928	805
Addition of Proved Undeveloped Locations [Member] | Proved Undeveloped Wolfcamp A locations [Member]
Proved Developed and Undeveloped Reserves Extensions Discoveries and Additions, Location		27
Addition of Proved Undeveloped Locations [Member] | Third Bone Spring locations [Member]
Proved Developed and Undeveloped Reserves Extensions Discoveries and Additions, Location		4
Addition of Proved Undeveloped Locations [Member] | Wolfcamp B Locations [Member]
Proved Developed and Undeveloped Reserves Extensions Discoveries and Additions, Location		2
Addition of Proved Undeveloped Locations [Member] | McKenzie County, ND [Member]
Proved Developed and Undeveloped Reserves Extensions Discoveries and Additions, Location			8
Proved Developed and Undeveloped Reserves Extensions Discoveries and Additions, Energy			18
Continued Improvement in Well Production Results [Member] | McKenzie County, ND [Member]
Proved Developed and Undeveloped Reserves Revisions of Previous Estimates, Energy			5,005
Improved Performance [Member] | Ward County, TX [Member]
Proved Developed and Undeveloped Reserves Revisions of Previous Estimates, Energy			1,360
Under-performance of Hedgehog State 16-2H [Member] | Porcupine Field, Campbell County, WY [Member]
Proved Developed and Undeveloped Reserves Revisions of Previous Estimates, Energy			(670)
Shortened Economic Life Expectations [Member]
Proved Developed and Undeveloped Reserves Revisions of Previous Estimates, Energy			(2,271)
Development of New Austin Chalk Producer [Member] | Atascosa County, TX [Member]
Proved Developed and Undeveloped Reserves Extensions Discoveries and Additions, Energy			265