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Taxation - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Giganology Shenzhen and Xunlei Computer [Member]      
Income Tax [Line Items]      
Withholding taxes on dividends paid $ 10    
PRC Enterprise [Member]      
Income Tax [Line Items]      
Effective income tax rate 25.00%    
High And New Technology Enterprises [Member] | Shenzhen Xunlei, Onething, Wangwenhua and Xunlei Computer      
Income Tax [Line Items]      
Preferential tax rate (as a percent) 15.00% 15.00% 15.00%
State Administration of Taxation, China [Member] | Research And Development Enterprise Activities [Member] | Shenzhen Xunlei [Member]      
Income Tax [Line Items]      
Portion of research and development expenses incurred that are allowable as tax deductible expenses (as a percent) 175.00%    
Domestic Tax Authority [Member]      
Income Tax [Line Items]      
Withholding tax rate on foreign enterprises 10.00%    
Withholding tax accrued or required to be accrued $ 0 $ 0 $ 0
Domestic Tax Authority [Member] | High And New Technology Enterprises [Member] | PRC Enterprise [Member]      
Income Tax [Line Items]      
Preferential tax rate (as a percent) 15.00%    
Domestic Tax Authority [Member] | Software Enterprise [Member] | PRC Enterprise [Member]      
Income Tax [Line Items]      
Period of full exemption from income tax 2 years    
Period of 50% reduction to income tax rate 3 years    
Domestic Tax Authority [Member] | National Key Software Enterprise [Member] | PRC Enterprise [Member]      
Income Tax [Line Items]      
Preferential tax rate (as a percent) 10.00%    
Foreign Tax Authority [Member] | Cayman Islands Tax Information Authority [Member]      
Income Tax [Line Items]      
Withholding taxes on dividends paid $ 0