XML 52 R39.htm IDEA: XBRL DOCUMENT v3.22.1
Summary of significant accounting policies, Allowance for doubtful accounts (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Allowance for doubtful accounts [Roll Forward]    
Balance, beginning of period $ 220 $ 221
Additions charged to costs and expenses 0 1
Deductions (1) (2)
Balance, end of period $ 219 $ 220