Acquisition - Additional Information (Detail) - USD ($)			6 Months Ended
	Jan. 02, 2020	Sep. 19, 2019	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Business Acquisition [Line Items]
Fair value of total loans			$ 447,702,000
Fair value of purchased credit impaired loans			39,320,000	$ 24,582,000	$ 26,408,000
Contractual amounts			53,588,000	$ 33,949,000	35,235,000
Purchased Credit Impaired Loans [Member]
Business Acquisition [Line Items]
Contractual amounts			9,818,000		$ 750,000
FBC Bancshares, Inc. and First Bank, N.A. [Member]
Business Acquisition [Line Items]
Payment for all outstanding shares of acquired entity by shares		6,275,574
Total loans of contractual amounts			455,181,000
FBC Bancshares, Inc. and First Bank, N.A. [Member] | Purchased Credit Impaired Loans [Member]
Business Acquisition [Line Items]
Fair value of purchased credit impaired loans			7,517,000
Contractual amounts			$ 10,061,000
Commercial Bancshares, Inc [Member]
Business Acquisition [Line Items]
Business acquisition, agreement date			Sep. 19, 2019
Payment for all outstanding shares of acquired entity by shares	6,275,574
Business acquisition, special dividend	$ 1,920,000