Acquisition and Asset Purchase - Additional Information (Detail) - USD ($)			9 Months Ended
	Aug. 03, 2015	Jul. 31, 2015	Sep. 30, 2015	Apr. 08, 2015	Dec. 31, 2014	Sep. 30, 2014
Business Acquisition [Line Items]
Fair value of purchased credit impaired loans			$ 21,788,000		$ 20,194,000	$ 22,093,000
Contractual amounts			$ 3,213,000		$ 3,275,000	$ 3,525,000
FBC Bancshares, Inc. and First Bank, N.A. [Member]
Business Acquisition [Line Items]
Business acquisition, agreement date			Apr. 01, 2015
Payment for all outstanding shares of acquired entity by shares		1,755,374
Subordinated debt, paid off	$ 13,125,000
Fair value of total loans			$ 248,380,000
Total loans of contractual amounts			252,458,000
Fair value of purchased credit impaired loans			1,398,000
Contractual amounts			$ 1,704,000
4Trust Mortgage, Inc. [Member]
Business Acquisition [Line Items]
Business acquisition, asset purchase agreement date			Apr. 08, 2015
Business acquisition, cash purchase price				$ 1,900,000