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Benefit plans (Details) - USD ($) | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2020 | Sep. 30, 2019 | Sep. 30, 2020 | Sep. 30, 2019
United States | 401(k) Plan |  |  |  |
Benefit plans |  |  |  |
Contributions made | $ 34,000 | $ 26,000 | $ 100,000 | $ 100,000
Foreign Plan | U.K. Plan |  |  |  |
Benefit plans |  |  |  |
Contributions made | $ 100,000 | $ 100,000 | $ 300,000 | $ 200,000

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- Definition Amount of cost for defined contribution plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Details
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