Note 1 - Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2020

Notes Tables

Schedule of Asset Retirement Obligations [Table Text Block]

	Year Ended December 31,
	2020			2019
Balance, beginning of year	$	15,764		$	14,646
Accretion		1,381			1,272
Revisions		—			95
Payments		(868	)		(249	)
Balance, end of year		16,277			15,764
Less current portion		(100	)		(70	)
Long-term balance, end of year	$	16,177		$	15,694