Selected Balance Sheet Data - Schedule of Other Assets (Parenthetical) (Detail) - USD ($) $ in Thousands  | 
3 Months Ended | |
|---|---|---|
Mar. 31, 2021  | 
Mar. 31, 2020  | 
|
| Other Assets [Line Items] | ||
| Reduction of accrued bonuses and other employee related expenses in settlement of employee notes receivable | $ 10 | $ 0 | 
| X | ||||||||||
- Definition Other Assets [Line Items] No definition available. 
  | 
| X | ||||||||||
- Definition Reduction of accrued bonuses and other employee related expenses in settlement of employee notes receivable. No definition available. 
  |