Investment Securities - Gross Unrealized Losses and Fair Value, Aggregated by Investment Category (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	$ 44,575	$ 60,388
Less Than 12 Months, Unrealized Losses	(829)	(81)
12 Months or More, Fair Value	78,854	80,431
12 Months or More, Unrealized Losses	(1,258)	(2,268)
Fair Value, Total	123,429	140,819
Gross Unrealized Losses	(2,087)	(2,349)
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	23,331	60,388
Less Than 12 Months, Unrealized Losses	(5)	(81)
12 Months or More, Fair Value	78,848	80,426
12 Months or More, Unrealized Losses	(1,257)	(2,267)
Fair Value, Total	102,179	140,814
Gross Unrealized Losses	(1,262)	(2,348)
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	21,244	0
Less Than 12 Months, Unrealized Losses	(824)	0
12 Months or More, Fair Value	6	5
12 Months or More, Unrealized Losses	(1)	(1)
Fair Value, Total	21,250	5
Gross Unrealized Losses	$ (825)	$ (1)