Severance and Retention - Summary of Severance Related Liabilities within Accounts Payable and Accrued Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Restructuring And Related Activities [Abstract]
Balance at beginning of year	$ 555	$ 1,071
Payments	(1,600)	(1,939)
Expense	1,403	1,423
Balance at ending of year	$ 358	$ 555