Fair Value of Financial Instruments - Summary of Financial Instruments Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Liabilities
Contingent liability for Essentialis purchase price	$ 5,938	$ 5,649
2017 PIPE Warrant Liability [Member]
Liabilities
Warrant liability	10,822	4,563
2018 PIPE Warrant Liability [Member]
Liabilities
Warrant liability	1,354	600
Series A Warrant Liability [Member]
Liabilities
Warrant liability		49
Fair Value, Measurements, Recurring [Member]
Liabilities
Total common stock warrant and contingent consideration liability	18,114	10,861
Fair Value, Measurements, Recurring [Member] | Derivative Financial Instruments, Liabilities | 2017 PIPE Warrant Liability [Member]
Liabilities
Warrant liability	10,822	4,563
Fair Value, Measurements, Recurring [Member] | Derivative Financial Instruments, Liabilities | 2018 PIPE Warrant Liability [Member]
Liabilities
Warrant liability	1,354	600
Fair Value, Measurements, Recurring [Member] | Derivative Financial Instruments, Liabilities | Series A Warrant Liability [Member]
Liabilities
Warrant liability		49
Essentialis, Inc. [Member] | Fair Value, Measurements, Recurring [Member]
Liabilities
Contingent liability for Essentialis purchase price	5,938	5,649
Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Liabilities
Total common stock warrant and contingent consideration liability		49
Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Derivative Financial Instruments, Liabilities | Series A Warrant Liability [Member]
Liabilities
Warrant liability		49
Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Liabilities
Total common stock warrant and contingent consideration liability	18,114	10,812
Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Derivative Financial Instruments, Liabilities | 2017 PIPE Warrant Liability [Member]
Liabilities
Warrant liability	10,822	4,563
Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Derivative Financial Instruments, Liabilities | 2018 PIPE Warrant Liability [Member]
Liabilities
Warrant liability	1,354	600
Level 3 [Member] | Essentialis, Inc. [Member] | Fair Value, Measurements, Recurring [Member]
Liabilities
Contingent liability for Essentialis purchase price	$ 5,938	$ 5,649