Consolidated balance sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Consolidated balance sheets
Accounts receivable, allowance	$ 2	$ 0
Ordinary shares, par value	$ 0.00006	$ 0.00006
Ordinary shares, shares authorized	83,333,333	83,333,333
Ordinary shares, shares issued	74,882,338	68,237,247
Ordinary shares, shares outstanding	74,882,338	68,237,247

Amount of allowance for credit loss on accounts receivable, classified as current.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Face amount or stated value per share of common stock.

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