Note 13 - Asset Retirement Obligation (Tables)

12 Months Ended

Dec. 31, 2023

Notes Tables

Schedule of Asset Retirement Obligations [Table Text Block]

	Year Ended December 31,
	2023		2022			2021
	(Dollars in thousands)
Balance at beginning of year	$	97,660	$	84,891		$	63,457
Revision in estimated cash flows		2,056		(1,802	)		10,504
Liabilities incurred and acquired		8,490		9,314			6,953
Accretion expense		6,164		5,257			3,977
Balance at end of year	$	114,370	$	97,660		$	84,891