Preferred stock warrants - Weighted Average of the Unobservable Inputs Used to Fair Value (Details)	3 Months Ended	6 Months Ended
	Jun. 30, 2021 Y $ / shares	Jun. 30, 2021 Y $ / shares
Remaining contractual term (in years)
Class of Warrant or Right [Line Items]
Preferred stock warrant liability, measurement input | Y	6.7	6.8
Risk-free interest rate
Class of Warrant or Right [Line Items]
Preferred stock warrant liability, measurement input	0.011	0.012
Expected volatility
Class of Warrant or Right [Line Items]
Preferred stock warrant liability, measurement input	0.422	0.419
Series A1 Redeemable Convertible Preferred Stock
Class of Warrant or Right [Line Items]
Fair value of preferred stock warrant liability	$ 2.51	$ 2.52
Series B1 Redeemable Convertible Preferred Stock
Class of Warrant or Right [Line Items]
Fair value of preferred stock warrant liability	2.88	2.89
Series C1 Redeemable Convertible Preferred Stock
Class of Warrant or Right [Line Items]
Fair value of preferred stock warrant liability	$ 2.95	$ 2.96