Investment Securities - Summary of Amortized Cost and Approximate Fair Value of Investment Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 557,621	$ 568,550
Gross Unrealized Gains	5,147	1,773
Gross Unrealized Losses	(6,603)	(10,070)
Fair Value	556,165	560,253
Corporate notes
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	44,927	39,925
Gross Unrealized Gains	303	320
Gross Unrealized Losses	(209)	(178)
Fair Value	45,021	40,067
Agency-guaranteed residential mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	285,259	299,392
Gross Unrealized Gains	2,359	1,453
Gross Unrealized Losses	(1,329)	(2,741)
Fair Value	286,289	298,104
Agency-guaranteed commercial real estate mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	204,921	206,719
Gross Unrealized Gains	2,485	0
Gross Unrealized Losses	(9)	(3,849)
Fair Value	207,397	202,870
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	22,514	22,514
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(5,056)	(3,302)
Fair Value	$ 17,458	$ 19,212

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=65884222&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
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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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-Publisher FASB
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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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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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