Income Taxes - Summary of Current and Deferred Components of Income Tax Expense (Benefit) (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current expense:
Federal									$ 2,548	$ 2,637	$ 3,628
State									697	697	412
Total current expense									3,245	3,334	4,040
Deferred (benefit) expense:
Federal									(1,660)	(1,238)	6,496
State									(367)	(528)	422
Valuation Allowance									(108)
Total deferred (benefit) expense									(2,135)	(1,766)	6,918
Provision for income taxes	$ 526	$ 435	$ 267	$ (118)	$ 309	$ 444	$ 314	$ 501	$ 1,110	$ 1,568	$ 10,958