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Commitments and Contingencies - Additional Information (Detail)
12 Months Ended
Dec. 31, 1987
lease
lease_extension
lease_renewal
Mar. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Commitment And Contingencies [Line Items]      
Outstanding warranty insurance receivables   $ 37,519,000 $ 37,597,000
Estimated remaining liabilities related to surety bonds   13,600,000 33,367,000
Surety bonds      
Commitment And Contingencies [Line Items]      
Outstanding surety bonds   653,900,000 685,700,000
Estimated remaining liabilities related to surety bonds   415,200,000 423,400,000
Legal Reserve      
Commitment And Contingencies [Line Items]      
Legal reserves   $ 0 $ 17,500,000
Office Leases      
Commitment And Contingencies [Line Items]      
Lease obligation original term   10 years  
Equipment Leases | Minimum      
Commitment And Contingencies [Line Items]      
Lease obligation original term   3 years  
Equipment Leases | Maximum      
Commitment And Contingencies [Line Items]      
Lease obligation original term   4 years  
Ground lease      
Commitment And Contingencies [Line Items]      
Lease obligation original term 55 years    
Number of properties subject to ground leases | lease 2    
Ten Year Renewal Option | Ground lease      
Commitment And Contingencies [Line Items]      
Number of lease extensions | lease_renewal 3    
Term of lease extension 10 years    
Forty-five Year Renewal Option | Ground lease      
Commitment And Contingencies [Line Items]      
Lease obligation original term 45 years    
Number of properties subject to ground leases | lease 1    
Extension Through 2071 | Ground lease      
Commitment And Contingencies [Line Items]      
Number of ground leases extended | lease_extension 1