Summary of Significant Accounting Policies - Narrative (Details)	3 Months Ended	12 Months Ended
Mar. 31, 2021 USD ($) segment	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)
Disaggregation of Revenue [Line Items]
Number of reportable segments \| segment	1
Number of operating segments \| segment	1
Product revenue	$ 6,611,000	$ 2,300,000
Product warranty, term	2 years
Sales commissions	$ 300,000	0
Contract assets	0		$ 0
Restricted cash	1,300,000		1,300,000
Restricted cash, current	276,000	276,000	276,000
Restricted cash, non-current	$ 1,004,000	$ 1,280,000	$ 1,004,000
Threshold period past due	90 days
Purchase \| Supplier Concentration Risk \| One Supplier
Disaggregation of Revenue [Line Items]
Concentration risk, percentage	11.00%	17.00%
Accounts Payable \| Supplier Concentration Risk \| One Supplier
Disaggregation of Revenue [Line Items]
Concentration risk, percentage		48.00%	23.00%
Product \| Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Product revenue	$ 6,600,000	$ 2,300,000

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Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

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