Summary of Significant Accounting Policies - Deferred tax assets (liabilities) (Details) - USD ($) $ in Thousands		Dec. 31, 2024	Dec. 31, 2023
Deferred tax assets (liabilities)
Basis differences		$ 26,620	$ 31,838
Deferred expense		461	949
Depreciation		665	1,101
Operating loss carryforwards	[1]	21,541	9,832
Mark-to-market cost method investments		33,369	16,926
Capitalized expenses		7,803	5,044
Valuation allowance		(90,459)	(65,690)
Net deferred tax assets (liabilities)		$ 0	$ 0

[1] The net operating loss (“NOL”) carryforwards can generally be used to offset both ordinary taxable income and capital gain net income in future years and are carried forward indefinitely. The deduction for NOL’s is limited to 80% of taxable income when utilized.