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Commitments and contingencies - Non-cancelable operating leases (Details) | 12 Months Ended
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Dec. 31, 2020 USD ($)
Auburn Washington [Member] |
Rent Expense [Line Items] |
Rent expense | $ 60,000
Lease Expiration Period Description | Month to Month
Baton Rouge Louisiana [Member] |
Rent Expense [Line Items] |
Rent expense | $ 24,600
Lease Expiration Period Description | Month to Month
Champaign Illinois [Member] |
Rent Expense [Line Items] |
Rent expense | $ 654,000
Lease Expiration Date | Dec. 01, 2024
Champaign, Illinois (2nd location) [Member] |
Rent Expense [Line Items] |
Rent expense | $ 305,000
Lease Expiration Date | Sep. 01, 2021
CharlotteNorthCarolina [Member] |
Rent Expense [Line Items] |
Rent expense | $ 31,000
Lease Expiration Date | May 01, 2021
EscondidoCalifornia [Member] |
Rent Expense [Line Items] |
Rent expense | $ 219,000
Lease Expiration Date | Jun. 01, 2022
HampsteadNewHampshireMember [Member] |
Rent Expense [Line Items] |
Rent expense | $ 33,000
Lease Expiration Date | Aug. 01, 2022
Long Beach California [Member] |
Rent Expense [Line Items] |
Rent expense | $ 27,600
Lease Expiration Date | Feb. 01, 2022
Long Island City New York [Member] |
Rent Expense [Line Items] |
Rent expense | $ 815,000
Lease Expiration Date | Jul. 01, 2021
OntarioCaliforniaMember [Member] |
Rent Expense [Line Items] |
Rent expense | $ 110,400
Lease Expiration Date | Dec. 01, 2021
Pearl River New York [Member] |
Rent Expense [Line Items] |
Rent expense | $ 150,000
Lease Expiration Date | Dec. 01, 2021
RiversideCaliforniaMember [Member] |
Rent Expense [Line Items] |
Rent expense | $ 27,000
Lease Expiration Period Description | Month to Month
Rantoul, Illinois [Member] |
Rent Expense [Line Items] |
Rent expense | $ 36,000
Lease Expiration Date | Feb. 01, 2021
SmyrnaGeorgiaMember [Member] |
Rent Expense [Line Items] |
Rent expense | $ 465,000
Lease Expiration Date | Jul. 01, 2030
StonyPointNyMember [Member] |
Rent Expense [Line Items] |
Rent expense | $ 105,000
Lease Expiration Date | Jun. 01, 2021

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- Definition Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income. + References Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=121573735&loc=d3e41499-112717 + Details
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