Quarterly report pursuant to Section 13 or 15(d)

Investments in Marketable Debt Securities, Available for Sale - Additional Information (Detail)

v3.21.2
Investments in Marketable Debt Securities, Available for Sale - Additional Information (Detail)
9 Months Ended 12 Months Ended
Sep. 30, 2021
USD ($)
Dec. 31, 2020
USD ($)
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale, securities in unrealized loss positions, accumulated loss $ 66,000 $ 50,000
Allowance for credit losses $ 0  
Weighted average contractual maturity 1 year 10 months 24 days 1 year 7 months 6 days
Fitch, AA Rating [Member] | Moody's, Aaa Rating [Member] | Standard & Poor's, AA Rating [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Weighted average contractual maturity 1 year 10 months 24 days  
Fitch, AA+ Rating [Member] | Moody's, Aa3 Rating [Member] | Standard & Poor's, AA+ Rating [Member] | Weighted Average Credit AA Plus Rating [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale, securities number of unrealized loss positions 37  
Available-for-sale, securities in unrealized loss positions, accumulated loss $ 66,000  
Percentage of amortized cost 0.10%