Segment Information - Summary of Segment Information (Parenthetical) (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Segment Reporting Information [Line Items]
Taxable-equivalent adjustment	$ 6,248,000	$ 5,841,000	$ 18,106,000	$ 17,635,000
Commercial Real Estate [Member]
Segment Reporting Information [Line Items]
Average assets		$ 246,000,000		$ 246,000,000
Residential Mortgage Banking [Member]
Segment Reporting Information [Line Items]
Average assets					$ 257,000,000