Note 8 - Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2020

Notes Tables

Schedule of Change in Asset Retirement Obligation [Table Text Block]

	As of December 31,
	2020			2019
Balance at Beginning of Period	$	271,952		$	267,001
Accretion Expense		17,905			20,116
Payments		(13,529	)		(13,030	)
Revisions in Estimated Cash Flows		(9,248	)		(2,135	)
Other		(18,311	)		—
Balance at End of Period	$	248,769		$	271,952