Financial instruments (Tables)

12 Months Ended

Dec. 31, 2021

Financial instruments

Schedule of Fair value hierarchy for assets and liabilities

	December 31, 2021
	Level 1		Level 2		Level 3		Total
Assets:
Recurring
Certificate of deposit	$	—	$	2,500,000	$	—	$	2,500,000
Net asset arising from put/call options		—		—		128,000		128,000

	December 31, 2020
	Level 1		Level 2		Level 3		Total
Liabilities:
Recurring
Net liability arising from put/call options	$	—	$	—	$	(690,000)	$	(690,000)

Schedule of Net liability arising from put/call options

Net (liability)/asset arising from put/call options
Balance as of December 31, 2020	$	(690,000)
Unrealized gain		818,000
Balance as of December 31, 2021	$	128,000