Note 1 - General and Basis of Presentation (Tables)

3 Months Ended

Mar. 31, 2023

Notes Tables

Schedule of Cash and Cash Equivalents [Table Text Block]

	March 31,		December 31,
	2023		2022
	(Dollars in thousands)
Cash and cash equivalents	$	414,856	$	95,872
Restricted cash and cash equivalents		107,466		130,804
Total Cash and cash equivalents and restricted cash and cash equivalents	$	522,322	$	226,676

Schedules of Concentration of Risk, by Risk Factor [Table Text Block]

	Three Months Ended March 31,
	2023			2022
Southern California Public Power Authority (“SCPPA”)		26.7	%		21.9	%
Sierra Pacific Power Company and Nevada Power Company		18.9			19.5
Kenya Power and Lighting Co. Ltd. ("KPLC")		14.5			14.1

Accounts Receivable, Allowance for Credit Loss [Table Text Block]

	Three Months Ended March 31,
	2023		2022
	(Dollars in thousands)
Beginning balance of the allowance for expected credit losses	$	90	$	90
Change in the provision for expected credit losses for the period		—		—
Ending balance of the allowance for expected credit losses	$	90	$	90

Contract with Customer, Contract Asset, Contract Liability, and Receivable [Table Text Block]

	March 31,			December 31,
	2023			2022
	(Dollars in thousands)
Contract assets (*)	$	17,136		$	16,405
Contract liabilities (*)	$	(24,651	)	$	(8,785	)

Operating Lease, Lease Income [Table Text Block]

	Three Months Ended March 31,
	2023		2022
	(Dollars in thousands)
Lease income relating to lease payments from operating leases	$	137,621	$	139,681