Commitments - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Schedule Of Commitments And Contingencies [Line Items]
Rent Expense	$ 1,706	$ 1,102	$ 946
Vehicle Lease
Schedule Of Commitments And Contingencies [Line Items]
Rent Expense	$ 779	$ 529	$ 555
Hannibal, Missouri \| Long-term Ground Lease
Schedule Of Commitments And Contingencies [Line Items]
Long Term Ground Leases Expiration Period	20 years
Minimum \| Axis, Alabama \| Long-term Ground Lease
Schedule Of Commitments And Contingencies [Line Items]
Long Term Ground Leases Expiration Period	20 years
Maximum \| Axis, Alabama \| Long-term Ground Lease
Schedule Of Commitments And Contingencies [Line Items]
Long Term Ground Leases Expiration Period	35 years