Revenue from Contracts with Customers (Tables)

9 Months Ended

Sep. 30, 2021

Revenue From Contract With Customer [Abstract]

Summary of Product and Service Revenue Disaggregated by Geographic Region

The following table summarizes the Company’s product and service revenue disaggregated by geographic region, which is determined based on customer location, for the three and nine months ended September 30, 2021 and 2020:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2021		2020		2021		2020
United States	$	3,521	$	3,119	$	10,901	$	7,559
South Korea		1,165		642		3,353		2,048
Europe		908		761		2,718		2,301
Asia (excluding South Korea)		1,278		1,463		2,453		3,447
Other		115		87		276		224
Total1	$	6,987	$	6,072	$	19,701	$	15,579

¹ The table above does not include lease revenue of $1,285 and $1,073 for three months ended September 30, 2021 and 2020, respectively, and $3,536 and $2,519 for the nine months ended September 30, 2021 and 2020, respectively. Substantially all lease revenue originates from the United States. Refer to Note 5, Leases.

Summary of Information about Receivables and Contract Liabilities from Contracts with Customers

The following table provides information about receivables and contract liabilities from contracts with customers:

	Classification	As of September 30, 2021		As of December 31, 2020
Accounts receivable, current	Accounts receivable, net	$	2,797	$	2,012
Notes receivable, current	Notes receivable, net	$	369	$	444
Notes receivable, long-term	Notes and other receivables, long-term, net	$	190	$	452
Contract liability, current	Deferred revenue	$	922	$	923
Contract liability, non-current	Other long-term liabilities	$	87	$	128

The following table provides information about contract liabilities from contracts with customers:

	Amount
Contract liabilities as of December 31, 2020	$	1,051
Billings not yet recognized as revenue		784
Beginning contract liabilities recognized as revenue		(826	)
Contract liabilities as of September 30, 2021	$	1,009
Contract liabilities as of December 31, 2019	$	895
Billings not yet recognized as revenue		658
Beginning contract liabilities recognized as revenue		(670	)
Contract liabilities as of September 30, 2020	$	883

Summary of Allowance for Accounts Receivable

The following table summarizes the activity in the allowance for accounts receivable:

	Amount
Accounts receivable, allowance for credit losses as of    December 31, 2020	$	19
Provision for credit losses		9
Write-offs		—
Accounts receivable, allowance for credit losses as of    September 30, 2021	$	28
Accounts receivable, allowance for credit losses as of    January 1, 2020	$	—
Impact of adoption of ASC 326		15
Provision for credit losses		28
Write-offs		(20	)
Accounts receivable, allowance for credit losses as of    September 30, 2020	$	23

Summary of Allowance for Notes Receivable

The following table summarizes the activity in the allowance for notes receivable:

	Amount
Notes receivable, allowance for credit losses as of    December 31, 2020	$	18
Provision for credit losses		(6	)
Write-offs		—
Notes receivable, allowance for credit losses as of    September 30, 2021	$	12
Notes receivable, allowance for credit losses as of    January 1, 2020	$	—
Impact of adoption of ASC 326	19
Provision for credit losses		1
Write-offs		—
Notes receivable, allowance for credit losses as of    September 30, 2020	$	20