Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Jul. 15, 2020	Jul. 14, 2020	Jan. 01, 2019
Summary Of Significant Accounting Policies [Line Items]
Common stock, shares authorized	100,000,000		100,000,000		100,000,000
Proceeds from sale of common stock			$ 56,682,000	$ 15,652,000
Restricted cash used to collateralize a credit card	$ 150,000		150,000		$ 150,000
Operating lease, right-of-use asset	7,876,000		7,876,000		5,337,000
Operating lease, liability	8,202,000		8,202,000
Cash equivalents	37,813,000		37,813,000		39,304,000
Short-term marketable securities	20,074,000		20,074,000		15,120,000
ASU 2016-02
Summary Of Significant Accounting Policies [Line Items]
Operating lease, right-of-use asset	7,876,000		7,876,000		$ 5,337,000			$ 9,692,000
Operating lease, liability								$ 9,347,000
General and Administrative Expense
Summary Of Significant Accounting Policies [Line Items]
Patent expenses	$ 245,000	$ 476,000	$ 1,586,000	$ 1,323,000
Type of Cost, Good or Service [Extensible List]	us-gaap:LicenseMember	us-gaap:LicenseMember	us-gaap:LicenseMember	us-gaap:LicenseMember
Trademarks
Summary Of Significant Accounting Policies [Line Items]
Useful life of trademark			15 years
Amortization of intangible assets	$ 2,916,000	$ 2,916,000	$ 8,750,000	$ 8,750,000
Stifel Nicolaus and Company Inc. | March 2020 ATM Agreement
Summary Of Significant Accounting Policies [Line Items]
Proceeds from sale of common stock, shares			1,824,901
Proceeds from sale of common stock	34,300,000		$ 34,300,000
Stifel Nicolaus and Company Inc. | March 2020 ATM Agreement | Maximum
Summary Of Significant Accounting Policies [Line Items]
Proceeds from sale of common stock			$ 35,000,000
Stifel Nicolaus and Company Inc. | Sales Agreement June 2020
Summary Of Significant Accounting Policies [Line Items]
Proceeds from sale of common stock, shares			1,192,000
Proceeds from sale of common stock	$ 22,400,000		$ 22,400,000
Stifel Nicolaus and Company Inc. | Sales Agreement June 2020 | Maximum
Summary Of Significant Accounting Policies [Line Items]
Proceeds from sale of common stock			$ 40,000,000
Stifel Nicolaus and Company Inc. | June 2019 ATM Agreement
Summary Of Significant Accounting Policies [Line Items]
Proceeds from sale of common stock, shares					3,584,945
Proceeds from sale of common stock					$ 29,400,000
Stifel Nicolaus and Company Inc. | June 2019 ATM Agreement | Maximum
Summary Of Significant Accounting Policies [Line Items]
Proceeds from sale of common stock					$ 30,000,000
Stifel Nicolaus and Company Inc. | November 2019 ATM Agreement
Summary Of Significant Accounting Policies [Line Items]
Proceeds from sale of common stock, shares					1,729,110
Proceeds from sale of common stock					$ 19,600,000
Stifel Nicolaus and Company Inc. | November 2019 ATM Agreement | Maximum
Summary Of Significant Accounting Policies [Line Items]
Proceeds from sale of common stock					$ 20,000,000
Common Stock
Summary Of Significant Accounting Policies [Line Items]
Common stock, shares authorized						100,000,000	50,000,000
Proceeds from sale of common stock, shares	842,000	1,560,541	3,016,901	2,084,615