Registration of securities issued in business combination transactions

The following table summarizes the estimated fair value of our investments, designated as available-for-sale and classified by the contractual maturity date (Details)

v3.21.4
The following table summarizes the estimated fair value of our investments, designated as available-for-sale and classified by the contractual maturity date (Details) - USD ($)
Sep. 30, 2021
Dec. 31, 2020
Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]      
Estimated Market Value $ 39,043,000 $ 18,393,000 $ 18,461,000
Investments [Member]      
Debt Securities, Available-for-sale [Line Items]      
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Amortized Cost 2,860,000 2,759,000  
Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, Year One 2,861,000 2,759,000  
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Amortized Cost 3,043,000 6,204,000  
Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year One Through Five 3,044,000 6,210,000  
Amortized Cost 5,903,000 8,963,000  
Estimated Market Value $ 5,905,000 $ 8,969,000 $ 9,700,000