Business combination - Additional Information (Details) $ / shares in Units, shares in Thousands, $ in Thousands	Mar. 05, 2020 USD ($) $ / shares shares	Sep. 30, 2021 $ / shares	Dec. 31, 2020 $ / shares
Business Acquisition [Line Items]
Common stock, par value (in dollars per share) | $ / shares	$ 0.0001	$ 0.0001	$ 0.0001
Acquisition related costs | $	$ 4,700
Additional Paid-In-Capital, Reduction Of Proceeds
Business Acquisition [Line Items]
Acquisition related costs | $	4,100
General and administrative
Business Acquisition [Line Items]
Acquisition related costs | $	$ 600
ChaSerg
Business Acquisition [Line Items]
Stock redeemed, price per share (in usd per share) | $ / shares	$ 10.21
GDI | ChaSerg
Business Acquisition [Line Items]
Number of common stock shares acquired (in shares)	50,800
Common stock, par value (in dollars per share) | $ / shares	$ 0.0001
Number of warrants acquired (in shares)	11,300
Consideration transferred | $	$ 396,459
Payments to acquire business | $	$ 130,000
Shares transferred at closing (in shares)	27,006
Price per share (in usd per share) | $ / shares	$ 10.19
Post closing share adjustment (in shares)	857
Options, vested, outstanding and unexercised (in shares)	4,300
Earnout shares vested (in shares)	1,700
Options, vested, exchange ratio	248.00%
Options, nonvested, outstanding and unexercised (in shares)	400
Earnout shares, nonvested (in shares)	100
Options, nonvested, exchange ratio	248.00%
Stock redeemed (in shares)	100
GDI | ChaSerg | Adjustment
Business Acquisition [Line Items]
Exchange ratio	1.685
2017 Acquisition | Cost Of Revenue and Operating Expenses
Business Acquisition [Line Items]
Acquisition related costs | $	$ 3,400