Shareholders' Equity - Company's Shares of Common Stock Reserved for Issuance (Detail) - shares	Jun. 30, 2022	Dec. 31, 2021
Class Of Warrant Or Right [Line Items]
Total shares reserved	46,014,655	46,299,718
April 2017 Warrants [Member]
Class Of Warrant Or Right [Line Items]
Total shares reserved	24,725	24,725
June 2017 Warrants [Member]
Class Of Warrant Or Right [Line Items]
Total shares reserved	41,736	41,736
December 2018 Warrants [Member]
Class Of Warrant Or Right [Line Items]
Total shares reserved	11,332	11,332
2017 Pre-Funded Warrants [Member]
Class Of Warrant Or Right [Line Items]
Total shares reserved	775,000	775,000
Pre-Funded PIPE Warrants [Member]
Class Of Warrant Or Right [Line Items]
Total shares reserved	5,780,537	5,780,537
2021 Pre-funded Warrants [Member]
Class Of Warrant Or Right [Line Items]
Total shares reserved	32,175,172	32,175,172
Stock Options Outstanding [Member]
Class Of Warrant Or Right [Line Items]
Total shares reserved	6,064,278	6,218,841
Issued and nonvested RSUs [Member]
Class Of Warrant Or Right [Line Items]
Total shares reserved	1,141,875	1,272,375