Summary of Significant Accounting Policies - Additional Information (Detail)	Sep. 30, 2020 USD ($)
ASU 2018-13 [Member]
Schedule Of Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adoption date	Jan. 01, 2020
Change in accounting principle, accounting standards update, early adoption	false
Change in accounting principle, accounting standards update, adopted	true
Change in accounting principle, accounting standards update, immaterial effect	true
Essentialis, Inc. [Member] | Earnout Payments [Member]
Schedule Of Significant Accounting Policies [Line Items]
Maximum potential cash earnout payments	$ 30,000,000