Investment Securities - Summary of Amortized Cost and Approximate Fair Value of Investment Securities (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 393,978	$ 414,928
Gross Unrealized Gains	4,303	4,106
Gross Unrealized Losses	(2,087)	(2,349)
Fair Value	396,194us-gaap_AvailableForSaleSecurities	416,685us-gaap_AvailableForSaleSecurities
Corporate notes
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		15,000
Gross Unrealized Gains		104
Gross Unrealized Losses		0
Fair Value		15,104
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	355,904	376,854
Gross Unrealized Gains	4,075	2,805
Gross Unrealized Losses	(1,262)	(2,348)
Fair Value	358,717	377,311
Corporate Bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	15,000
Gross Unrealized Gains	172
Gross Unrealized Losses	0
Fair Value	15,172
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	23,074	23,074
Gross Unrealized Gains	56	1,197
Gross Unrealized Losses	(825)	(1)
Fair Value	$ 22,305	$ 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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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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