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Commitments and contingencies - Non-cancelable operating leases (Details) - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020
Rent Expense [Line Items] |  |
Rent expense | $ 3,100,000 | $ 3,000,000.0
Auburn Washington [Member] |  |
Rent Expense [Line Items] |  |
Rent expense | $ 36,000 |
Lease Expiration Date | Apr. 01, 2022 |
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 | $ 349,000 |
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 | $ 28,800 |
Lease Expiration Date | Feb. 01, 2022 |
OntarioCaliforniaMember [Member] |  |
Rent Expense [Line Items] |  |
Rent expense | $ 168,000 |
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 Period Description | 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 |
Woodcliff Lake, New Jersey |  |
Rent Expense [Line Items] |  |
Rent expense | $ 158,000 |
Lease Expiration Date | Aug. 01, 2027 |

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- Definition Date which lease or group of leases is set to expire, in YYYY-MM-DD format. + References No definition available. + Details
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- Definition Amount of operating lease expense. Excludes sublease income. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 45 -Paragraph 4 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123391704&loc=SL77918638-209977 + Details
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