Related-Party Transactions (Tables)

12 Months Ended

Dec. 31, 2020

Related Party Transactions [Abstract]

Summary of Terms of Letter Agreements

Certain terms of these Letter Agreements are set forth in the tables below:  

	December 5, 2017 Letter Agreement		July 30, 2018 Letter Agreement		December 11, 2018 Letter Agreement
Aggregate dollar value to be    sold under agreement	$10.0 million		$10.0 million		$10.0 million
Specified purchase price    per share	$	4.38	$	1.33	$	1.84
Expiration date of letter    agreement	December 5, 2018		July 30, 2019		December 11, 2019
Shares available to be issued    under related warrants		198,267		518,654		340,534
Exercise price of related    warrants	$	5.04	$	1.53	$	2.12
Expiration date of related    warrants	December 5, 2024		July 30, 2025		December 11, 2025
Total shares issued as of    December 31, 2020		2,283,105		7,518,797		5,434,783
Remaining shares to be issued    as of December 31, 2020		—		—		—

	March 18, 2019 Letter Agreement		September 26, 2019 Letter Agreement		December 23, 2019 Letter Agreement
Aggregate dollar value to be    sold under agreement	$9.0 million		$10.0 million		$10.0 million
Specified purchase price    per share	$	1.65	$	1.46	$	1.60
Expiration date of letter    agreement	March 18, 2020		September 26, 2020		December 23, 2020
Shares available to be issued    under related warrants		—		400,990		365,472
Exercise price of related    warrants	$	—	$	1.68	$	1.84
Expiration date of related    warrants			September 26, 2026		December 23, 2026
Total shares issued as of    December 31, 2020		5,454,546		6,849,316		6,250,000
Remaining shares to be issued    as of December 31, 2020		—		—		—