Annual report pursuant to Section 13 and 15(d)

Notes Payable - Additional Information (Details)

v3.21.1
Notes Payable - Additional Information (Details) - USD ($)
1 Months Ended
Jul. 31, 2020
Sep. 30, 2019
Jan. 31, 2014
Dec. 31, 2020
Sep. 30, 2020
Jun. 30, 2020
Dec. 31, 2019
Jul. 31, 2018
Jul. 31, 2017
Term Note                  
Debt Instrument [Line Items]                  
Unused facility fee percentage   0.375%              
Line of credit facility, maximum borrowing capacity   $ 150,000,000.0              
Maximum amount of committed to increase   $ 78,000,000.0              
Long-term Line of Credit       $ 80,800,000     $ 78,000,000.0    
Debt instrument maturity date   Sep. 30, 2022              
Debt Instrument, Periodic Payment, Principal, Percentage of Outstanding Balance         5.00%        
New Term Note                  
Debt Instrument [Line Items]                  
Maximum amount of committed to increase   $ 100,000,000.0              
Federal Funds Rate | Term Note                  
Debt Instrument [Line Items]                  
Debt instrument variable rate   0.50%              
Eurodollar Base Rate | Term Note                  
Debt Instrument [Line Items]                  
Debt instrument variable rate   1.00%              
Government National Mortgage Association | Revolving Credit Facility                  
Debt Instrument [Line Items]                  
Unused facility fee percentage     70.00%            
Line of credit facility, maximum borrowing capacity           $ 135,000,000.0      
Maximum amount of committed to increase           $ 200,000,000.0      
Long-term Line of Credit       45,000,000.0     90,000,000.0    
Government National Mortgage Association | LIBOR | Revolving Credit Facility                  
Debt Instrument [Line Items]                  
Line of credit, floor interest rate     4.50%            
Federal Home Loan Mortgage Corporation | Revolving Credit Facility                  
Debt Instrument [Line Items]                  
Unused facility fee percentage 50.00%                
Line of credit facility, maximum borrowing capacity $ 65,000,000.0             $ 50,000,000.0 $ 25,000,000.0
Long-term Line of Credit       $ 20,000,000.0     $ 50,000,000.0    
Federal Home Loan Mortgage Corporation | LIBOR | Revolving Credit Facility                  
Debt Instrument [Line Items]                  
Line of credit, floor interest rate 0.75%