XML 53 R43.htm IDEA: XBRL DOCUMENT v3.19.2
Australia Research and Development Tax Incentive - Additional Information (Detail) - USD ($)
3 Months Ended 6 Months Ended 12 Months Ended
Jan. 01, 2019
Jun. 30, 2019
Jun. 30, 2018
Jun. 30, 2019
Jun. 30, 2018
Dec. 31, 2018
Research and Development Tax Incentive [Line Items]            
Unrealized foreign currency exchange losses       $ 5,000 $ 74,000  
Zafgen Australia Pty Limited [Member]            
Research and Development Tax Incentive [Line Items]            
Unrealized foreign currency exchange losses     $ 100,000   100,000  
Zafgen Australia Pty Limited [Member] | Australia [Member]            
Research and Development Tax Incentive [Line Items]            
Tax incentive receivable   $ 1,700,000   1,700,000   $ 1,500,000
Zafgen Australia Pty Limited [Member] | Maximum [Member]            
Research and Development Tax Incentive [Line Items]            
Unrealized foreign currency exchange losses   100,000   100,000    
Research and Development [Member] | Zafgen Australia Pty Limited [Member]            
Research and Development Tax Incentive [Line Items]            
Percentage of refundable tax incentive 41.00%         43.50%
Reduction to research and development expenses   $ 100,000 $ 400,000 $ 200,000 $ 1,000,000  
Percentage of reduction in research and development costs       41.00% 43.50%