Nature of business and summary of significant accounting policies, Accounts receivable and allowance for doubtful accounts (Details) - USD ($) $ in Millions |
Dec. 31, 2019 |
Dec. 31, 2018 |
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| Accounts receivable and allowance for doubtful accounts [Abstract] | ||
| Allowance for doubtful accounts | $ 0.0 | |
| Maximum [Member] | ||
| Accounts receivable and allowance for doubtful accounts [Abstract] | ||
| Allowance for doubtful accounts | $ 0.1 |
| X | ||||||||||
- References No definition available.
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| X | ||||||||||
- Definition Amount of allowance for credit loss on accounts receivable. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Details
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