Summary of Significant Accounting Policies - Additional Information (Details)	3 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Jan. 01, 2020 USD ($)	Oct. 04, 2018 ft²
Summary Of Significant Accounting Policies [Line Items]
Impairment of long-lived assets		$ 0
Contract liability balance, revenue recognized		1,200,000
Unrecognized tax benefit income tax interest and penalty charges		0
Accumulated deficit		304,684,000	$ 260,393,000	$ 205,825,000
San Francisco | Office Lease
Summary Of Significant Accounting Policies [Line Items]
Lease rentable area | ft²						117,560
Printed Circuit Board Assemblies
Summary Of Significant Accounting Policies [Line Items]
Other assets		$ 12,600,000	$ 7,400,000
Employee Severance | COVID-19 Disruption And Recovery
Summary Of Significant Accounting Policies [Line Items]
Employees furloughed (as a percent)	5.00%
Employees laid-off (as a percent)	2.00%
ASC 326 | Cumulative Effect, Period of Adoption, Adjustment
Summary Of Significant Accounting Policies [Line Items]
Accumulated deficit					$ 500,000
Allowance for doubtful accounts					$ 500,000
Internal-use software
Summary Of Significant Accounting Policies [Line Items]
Internal-use software, estimated useful life (in years)		5 years
Minimum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment, estimated useful life (in years)		3 years
Maximum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment, estimated useful life (in years)		5 years
Accounts Receivable | Accounts Receivable Concentration Risk | Federal Government Agencies
Summary Of Significant Accounting Policies [Line Items]
Concentration of credit risk (as a percent)		20.00%	20.00%
Revenue | Customer Concentration Risk | Federal Government Agencies
Summary Of Significant Accounting Policies [Line Items]
Concentration of credit risk (as a percent)		27.00%	27.00%	27.00%