Fair Value Measurements - Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Restricted cash:
Restricted cash	$ 600	$ 600
Short-term investments:
Total short-term investments		2,249
Recurring basis [Member]
Cash equivalents:
Total cash equivalents	5,855	3,620
Short-term investments:
Total short-term investments		2,249
Total assets measured at fair value	6,455	6,469
Corporate commercial paper [Member] | Recurring basis [Member]
Cash equivalents:
Total cash equivalents	1,748	999
Short-term investments:
Total short-term investments		748
Corporate debt [Member] | Recurring basis [Member]
Cash equivalents:
Total cash equivalents	500	750
Short-term investments:
Total short-term investments		1,501
Money market funds [Member] | Recurring basis [Member]
Cash equivalents:
Total cash equivalents	3,607	1,871
Restricted cash:
Restricted cash	600	600
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Recurring basis [Member]
Cash equivalents:
Total cash equivalents	3,607	1,871
Short-term investments:
Total assets measured at fair value	4,207	2,471
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Money market funds [Member] | Recurring basis [Member]
Cash equivalents:
Total cash equivalents	3,607	1,871
Restricted cash:
Restricted cash	600	600
Direct or Indirect Observable Inputs (Level 2) [Member] | Recurring basis [Member]
Cash equivalents:
Total cash equivalents	2,248	1,749
Short-term investments:
Total short-term investments		2,249
Total assets measured at fair value	2,248	3,998
Direct or Indirect Observable Inputs (Level 2) [Member] | Corporate commercial paper [Member] | Recurring basis [Member]
Cash equivalents:
Total cash equivalents	1,748	999
Short-term investments:
Total short-term investments		748
Direct or Indirect Observable Inputs (Level 2) [Member] | Corporate debt [Member] | Recurring basis [Member]
Cash equivalents:
Total cash equivalents	$ 500	750
Short-term investments:
Total short-term investments		$ 1,501