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Commitments and Contingencies - Additional Information (Detail)
12 Months Ended
Dec. 31, 1987
lease_extension
lease_renewal
lease
Sep. 30, 2021
USD ($)
Dec. 31, 2020
USD ($)
Commitment And Contingencies [Line Items]      
Legal reserves   $ 0 $ 1,300,000
Outstanding warranty insurance receivables   46,519,000 46,909,000
Estimated remaining liabilities related to surety bonds   $ 19,467,000 12,835,000
Office Leases      
Commitment And Contingencies [Line Items]      
Lease obligation original term   10 years  
Ground leases      
Commitment And Contingencies [Line Items]      
Lease obligation original term 55 years    
Number of properties subject to ground leases | lease 2    
Minimum | Equipment Leases      
Commitment And Contingencies [Line Items]      
Lease obligation original term   3 years  
Maximum | Equipment Leases      
Commitment And Contingencies [Line Items]      
Lease obligation original term   4 years  
Surety Bonds      
Commitment And Contingencies [Line Items]      
Outstanding surety bonds   $ 670,000,000 615,400,000
Estimated remaining liabilities related to surety bonds   $ 452,000,000 $ 323,200,000
Ten Year Renewal Option | Ground leases      
Commitment And Contingencies [Line Items]      
Number of lease extensions | lease_renewal 3    
Term of lease extension 10 years    
Forty-five Year Renewal Option | Ground leases      
Commitment And Contingencies [Line Items]      
Lease obligation original term 45 years    
Number of properties subject to ground leases | lease 1    
Extension Through 2071 | Ground leases      
Commitment And Contingencies [Line Items]      
Number of ground leases extended | lease_extension 1