Long-term debt (Tables)
 12 Months Ended
Dec. 31, 2019
Long-term Debt, Unclassified [Abstract]  
Schedule of future principal payments on the 2014 Term Loan
Future principal payments, including the End of Term Charges, are as follows (in thousands):
 
December 31,
 
2019
2020
$
—

2021
13,960

Total
$
13,960