Summary of significant accounting policies - Analysis of Different Types of Revenues (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net revenues
Product revenue	$ 8,269	$ 54,604	$ 32,894
Live streaming revenue	26,920	31,031	17,977
Total	181,267	232,132	201,911
Subscription and circulation [Member]
Net revenues
Revenue from Contract with Customer, Including Assessed Tax	81,532	81,877	84,956
Advertising [Member]
Net revenues
Revenue from Contract with Customer, Including Assessed Tax	15,643	27,781	22,484
Product and Service, Other [Member]
Net revenues
Revenue from Contract with Customer, Including Assessed Tax	$ 48,903	$ 36,839	$ 43,600

Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

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