Nature of business and summary of significant accounting policies - Advertising (Details) - USD ($) $ in Millions |
12 Months Ended | |
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Dec. 31, 2020 |
Dec. 31, 2019 |
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| Accounting Policies [Abstract] | ||
| Advertising expense | $ 5.8 | $ 6.7 |
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- References No definition available.
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- Definition Amount charged to advertising expense for the period, which are expenses incurred with the objective of increasing revenue for a specified brand, product or product line. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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