Revenue - Narrative (Details) $ in Thousands	3 Months Ended
Mar. 31, 2022 USD ($) performance_obligation	Mar. 31, 2021 USD ($)
Disaggregation of Revenue [Line Items]
Revenue	$ 1,082	$ 329
Prototype sales
Disaggregation of Revenue [Line Items]
Revenue	$ 335	233
Number of performance obligations \| performance_obligation	1
Development contracts
Disaggregation of Revenue [Line Items]
Revenue	$ 747	96
Revenue recognized for performance obligation satisfied	$ 747	$ 96

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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+ Details