Accounting for Certain Loans Acquired in a Transfer - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Business Acquisition [Line Items]
Total provision charged to operating expense	$ 896,000	$ 635,000	$ 1,260,000	$ 1,202,000
Loans Purchased With Evidence of Credit Deterioration [Member]
Business Acquisition [Line Items]
Total provision charged to operating expense			$ 154,000	$ 0