Income taxes (Reconciliation of Income Taxes) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Statutory federal income tax expense (benefit)	$ (1,611)	$ (2,660)	$ (4,293)
State taxes, net of federal tax expense (benefit)	347	(471)	(664)
Nondeductible/nontaxable items	1,732	(45)	1,142
Tax return to provision true-up	313	(8,737)
State tax rate change	(1,897)	2,231
Other			195
Change in valuation allowance	1,370	9,682	3,477
Income taxes expense (benefit)	$ 254		$ (143)