Note 12 - Subsequent Events (Details Textual) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended
Apr. 30, 2022	Mar. 31, 2022	Mar. 31, 2021
Payments to Acquire Equity Securities, FV-NI		$ 10,868	$ (0)
Equity Securities in Mining Companies [Member]
Payments to Acquire Equity Securities, FV-NI		$ 10,900	$ 0
Subsequent Event [Member] \| Equity Securities in Mining Companies [Member]
Payments to Acquire Equity Securities, FV-NI	$ 10,000

Amount of cash outflow to acquire investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI), classified as investing activity.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 45
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=123583714&loc=SL75117360-209713

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 19
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3444-108585

Name:	us-gaap_PaymentsToAcquireEquitySecuritiesFvNi
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration