Fair Value Measurements - Assets and Liabilities which are Measured at Fair Value on a Recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Assets
Total Assets	$ 24,225	$ 15,313
Liabilities
Total Liabilities		13,642
Convertible Debentures [Member]
Liabilities
Total Liabilities		13,642
Money Market Accounts [Member]
Assets
Total Assets	24,225	15,313
Level 1 [Member]
Assets
Total Assets	24,225	15,313
Level 1 [Member] | Money Market Accounts [Member]
Assets
Total Assets	$ 24,225	15,313
Level 3 [Member]
Liabilities
Total Liabilities		13,642
Level 3 [Member] | Convertible Debentures [Member]
Liabilities
Total Liabilities		$ 13,642