Note 9 - Supplemental Information Relating to Oil and Gas Producing Activities (Unaudited) - Changes in Standardized Measure of Discounted Future Net Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Balance, beginning of year	$ (8,211)	$ 28,157
Extensions, discoveries and other additions	85	30
Revision of quantity estimates	(184)	(2,562)
Sales of crude oil and natural gas, net of production costs	(1,274)	(2,993)
Net change in income taxes	32	573
Net changes in prices and production costs	(1,080)	(31,254)
Accretion of discount	(821)	2,816
Other	1,529	(2,978)
Balance, end of year	$ (9,924)	$ (8,211)