Indentifiable net assets (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Assets	$ 677,040	$ 678,190
Investments available for sale	0	4,317
Cash	160,027	162,273
Asset Management [Member]
Segment Reporting Information [Line Items]
Assets	24,340	23,897
Mining Properties [Member]
Segment Reporting Information [Line Items]
Assets	48,835	37,627
Development [Member]
Segment Reporting Information [Line Items]
Assets	175,925	176,386
Stabilized Joint Venture [Member]
Segment Reporting Information [Line Items]
Assets	261,594	266,429
Unallocated Corporate Assets [Member]
Segment Reporting Information [Line Items]
Assets	$ 6,319	$ 7,261