Summary of significant accounting policies - Additional information (Details)		3 Months Ended		12 Months Ended
	Apr. 21, 2021	Mar. 31, 2022 USD ($) segments	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($)
Accounting Policies [Line Items]
Number of operating segments | segments		1
Restricted cash		$ 100,000		$ 100,000
Unbilled receivables		900,000		800,000
Allowance for doubtful accounts		0		0
Impairment of goodwill		0		0
Consideration payables to customers		(200,000)	$ (100,000)
Research and development expense		200,000	1,300,000
Advertising expense		300,000	100,000
Contract with customer, liability		7,400,000		7,200,000
Remaining performance obligation, amount		25,200,000		31,400,000
Revenue recognized		2,000,000	800,000
Deferred revenue		7,181,000		8,450,000
Amortization expense		11,200	100,000
Impairment loss		$ 0	0
Percent of remaining performance obligations to be recognized as revenues next twelve months		61.30%
Accumulated other comprehensive income		$ 301,000		213,000
Total comprehensive loss		(48,061,000)	(65,171,000)
Series D
Accounting Policies [Line Items]
Proceeds from sale of equity			28,700,000
2Predict, Inc.
Accounting Policies [Line Items]
Definite-lived intangible asset, useful life	1 year 6 months
Finite-lived intangibles, amortization		200,000	0
Term loan
Accounting Policies [Line Items]
Less current maturities, net of unamortized debt issuance costs		100,000		100,000
Prepaid Expenses and Other Current Assets
Accounting Policies [Line Items]
Asset purchase		44,600		44,600
Other Noncurrent Assets
Accounting Policies [Line Items]
Asset purchase		300,000		300,000
Unbilled Revenues
Accounting Policies [Line Items]
Contract with customer, liability		900,000		$ 800,000
Construction in progress: stations
Accounting Policies [Line Items]
Other cost and expense		$ 300,000	$ 100,000