Annual report pursuant to Section 13 and 15(d)

Financial Instruments - Additional Information (Detail)

v3.20.4
Financial Instruments - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Financial Instruments Disclosure [Abstract]      
Accrued interest receivable $ 700,000 $ 900,000  
Write off, of accrued interest receivable 0 0 $ 0
Restricted Cash $ 1,400,000 $ 1,400,000