Fair value measurements (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Fair value measurements
Changes in estimates, and other	$ (44,000)	$ 142,000
Fair value Assumptions
Fair value adjustments to long lived assets	$ 0	$ 0
Fabled Copper Corp. | Sale, not discontinued operations | Binding Letter of Intent Agreement
Fair value Assumptions
Consideration received in shares | shares	200,000
Level 1 | Fabled Copper Corp. | Binding Letter of Intent Agreement
Fair value Assumptions
Investment shares held (in shares)		20,000
Fair Value, Measurements, Recurring
Fair value measurements
Cash and cash equivalents	$ 3,766,000	$ 3,972,000
Short-term investments	11,000	20,000
Assets	3,777,000	3,992,000
Fair Value, Measurements, Recurring | Level 1
Fair value measurements
Cash and cash equivalents	3,766,000	3,972,000
Short-term investments	11,000	20,000
Assets	$ 3,777,000	$ 3,992,000