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Commitments and contingencies - Additional Information (Detail)
¥ in Millions
1 Months Ended 12 Months Ended
Jan. 31, 2018
case
Dec. 31, 2021
USD ($)
case
Dec. 31, 2021
CNY (¥)
Dec. 31, 2020
USD ($)
Dec. 31, 2020
CNY (¥)
Dec. 31, 2019
USD ($)
Apr. 22, 2020
USD ($)
Loss Contingencies [Line Items]              
Legal and litigation related expenses   $ 997,000       $ 1,955,000  
Legal expense reversed       $ 1,217,000      
Number of lawsuits pending | case   17          
Legal and litigation related expenses   $ 973,000   1,640,000      
Putative Shareholder Class Action [Member]              
Loss Contingencies [Line Items]              
Claims filed during the period | case 2            
Pending Litigation [Member]              
Loss Contingencies [Line Items]              
Number of lawsuits pending | case   17          
Aggregate amount of claimed damages   $ 1,700,000 ¥ 10.9 1,900,000 ¥ 13.3    
Legal and litigation related expenses   $ 973,000   $ 1,640,000      
Pending Litigation [Member] | Copyright Infringement [Member]              
Loss Contingencies [Line Items]              
Number of lawsuits pending             9