Investment Securities - Gross Unrealized Losses and Fair Value, Aggregated by Investment Category (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	$ 95,785	$ 60,388
Less Than 12 Months, Unrealized Losses	(2,660)	(81)
12 Months or More, Fair Value	75,484	80,431
12 Months or More, Unrealized Losses	(2,929)	(2,268)
Fair Value, Total	171,269	140,819
Gross Unrealized Losses	(5,589)	(2,349)
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	75,517	60,388
Less Than 12 Months, Unrealized Losses	(421)	(81)
12 Months or More, Fair Value	75,478	80,426
12 Months or More, Unrealized Losses	(2,928)	(2,267)
Fair Value, Total	150,995	140,814
Gross Unrealized Losses	(3,349)	(2,348)
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	20,268	0
Less Than 12 Months, Unrealized Losses	(2,239)	0
12 Months or More, Fair Value	6	5
12 Months or More, Unrealized Losses	(1)	(1)
Fair Value, Total	20,274	5
Gross Unrealized Losses	$ (2,240)	$ (1)