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Commitments - Additional Information (Detail)
$ in Thousands
 12 Months Ended
Dec. 31, 2016
USD ($)
a
Dec. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
Schedule Of Commitments And Contingencies [Line Items]      
Rent Expense | $ $ 946 $ 947 $ 1,012
Hannibal, Missouri      
Schedule Of Commitments And Contingencies [Line Items]      
Long Term Ground Leases Expiration Period 20 years    
Marsing      
Schedule Of Commitments And Contingencies [Line Items]      
Long Term Ground Leases Expiration Period 25 years    
Number of acres owns | a 15    
Number of acres holds on long-term ground lease | a 2    
Vehicle Lease      
Schedule Of Commitments And Contingencies [Line Items]      
Rent Expense | $ $ 555 $ 435 $ 442
Minimum | Axis, Alabama      
Schedule Of Commitments And Contingencies [Line Items]      
Long Term Ground Leases Expiration Period 20 years    
Maximum | Axis, Alabama      
Schedule Of Commitments And Contingencies [Line Items]      
Long Term Ground Leases Expiration Period 35 years