Investment Securities - Summary of Amortized Cost and Approximate Fair Value of Investment Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 377,091	$ 414,928
Gross Unrealized Gains	2,451	4,106
Gross Unrealized Losses	(5,589)	(2,349)
Fair Value	373,953	416,685
Corporate notes
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	22,000	15,000
Gross Unrealized Gains	324	104
Gross Unrealized Losses	0	0
Fair Value	22,324	15,104
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	332,577	376,854
Gross Unrealized Gains	2,127	2,805
Gross Unrealized Losses	(3,349)	(2,348)
Fair Value	331,355	377,311
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	22,514	23,074
Gross Unrealized Gains	0	1,197
Gross Unrealized Losses	(2,240)	(1)
Fair Value	$ 20,274	$ 24,270

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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