Cash Value of Life Insurance - Summary of Activity in Balance of Cash Value of Life Insurance (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) Company Policies Employees	Dec. 31, 2018 USD ($) Company Policies Employees	Dec. 31, 2017 USD ($)	Jul. 06, 2018 USD ($)
Insurance [Line Items]
Beginning balance	$ 117,318	$ 97,783
Increase in cash value of life insurance	3,029	2,718	$ 2,685
Gain on death benefit	831
Insurance proceeds receivable reclassified to other assets	(3,355)
Ending balance	117,823	117,318	$ 97,783
End of period death benefit	$ 199,084	$ 200,249
Number of policies owned (in policies) | Policies	189	196
Insurance companies used (in companies) | Company	14	14
Current and former employees and directors covered (in employees) | Employees	63	66
FNBB
Insurance [Line Items]
Acquired policies from business combination	$ 0	$ 16,817		$ 16,817