The Company and a Summary of its Significant Accounting Policies - Additional Information (Details)		3 Months Ended
	Aug. 29, 2019	Mar. 31, 2020 USD ($) Revenue_Stream Segment shares	Mar. 31, 2019 USD ($) shares	Dec. 31, 2019 USD ($)
The Company and Summary of its Significant Accounting Policies [Line Items]
Conversion ratio of reverse stock split	0.5	0.5
Description of reverse stock split of common stock		one-for-two
Depreciation expense		$ 60,000	$ 19,000
Disposal of plant or equipment		0	0
Impairment losses		0	0
Bank deposits		67,900,000
Insured amount by FDIC		$ 250,000
Number of revenue streams | Revenue_Stream		2
Deferred revenue		$ 1,093,000		$ 1,390,000
Accounts receivable		$ 1,175,000		680,000
Number of operating segments | Segment		1
Stock-based compensation expense		$ 1,000,000	$ 300,000
Compensation cost related to non-vested awards not yet recognized		$ 7,800,000
Weighted average term expected to be recognized		2 years 11 months 15 days
Fair value other assets measured on recurring basis		$ 0
Fair value liabilities measured on recurring basis		$ 0
Conversion of Preferred Stock
The Company and Summary of its Significant Accounting Policies [Line Items]
Anti-dilutive equity instruments excluded from diluted net loss per common share | shares		4,338,136	1,524,122
Common Stock Warrants
The Company and Summary of its Significant Accounting Policies [Line Items]
Anti-dilutive equity instruments excluded from diluted net loss per common share | shares		4,212,349	685,761
Stock Options and Restricted Stock Units
The Company and Summary of its Significant Accounting Policies [Line Items]
Anti-dilutive equity instruments excluded from diluted net loss per common share | shares		1,342,625	1,574,655
Contract Revenue
The Company and Summary of its Significant Accounting Policies [Line Items]
Accounts receivable		$ 400,000		300,000
Assay Revenue
The Company and Summary of its Significant Accounting Policies [Line Items]
Accounts receivable gross		$ 800,000		$ 500,000
Minimum
The Company and Summary of its Significant Accounting Policies [Line Items]
Useful life of the assets		2 years
Minimum | Stock Options
The Company and Summary of its Significant Accounting Policies [Line Items]
Requisite service period		3 years
Minimum | Restricted Stock Units
The Company and Summary of its Significant Accounting Policies [Line Items]
Requisite service period		2 years
Maximum
The Company and Summary of its Significant Accounting Policies [Line Items]
Useful life of the assets		5 years
Maximum | Stock Options
The Company and Summary of its Significant Accounting Policies [Line Items]
Requisite service period		4 years
Maximum | Restricted Stock Units
The Company and Summary of its Significant Accounting Policies [Line Items]
Requisite service period		4 years