Investment Securities - Gross Unrealized Losses and Fair Value, Aggregated by Investment Category (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	$ 26,728	$ 60,388
Less Than 12 Months, Unrealized Losses	(4,779)	(81)
12 Months or More, Fair Value	67,270	80,431
12 Months or More, Unrealized Losses	(1,860)	(2,268)
Fair Value, Total	93,998	140,819
Gross Unrealized Losses	(6,639)	(2,349)
Corporate notes
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	8,871
Less Than 12 Months, Unrealized Losses	(129)
12 Months or More, Fair Value	0
12 Months or More, Unrealized Losses	0
Fair Value, Total	8,871
Gross Unrealized Losses	(129)
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	0	60,388
Less Than 12 Months, Unrealized Losses	0	(81)
12 Months or More, Fair Value	67,264	80,426
12 Months or More, Unrealized Losses	(1,859)	(2,267)
Fair Value, Total	67,264	140,814
Gross Unrealized Losses	(1,859)	(2,348)
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	17,857	0
Less Than 12 Months, Unrealized Losses	(4,650)	0
12 Months or More, Fair Value	6	5
12 Months or More, Unrealized Losses	(1)	(1)
Fair Value, Total	17,863	5
Gross Unrealized Losses	$ (4,651)	$ (1)