Investment Securities - Summary of Amortized Cost and Approximate Fair Value of Investment Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 568,550	$ 414,928
Gross Unrealized Gains	1,773	4,106
Gross Unrealized Losses	(10,070)	(2,349)
Investment securities available for sale, fair value	560,253	416,685
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	506,111	376,854
Gross Unrealized Gains	1,453	2,805
Gross Unrealized Losses	(6,590)	(2,348)
Investment securities available for sale, fair value	500,974	377,311
Corporate notes
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	39,925	15,000
Gross Unrealized Gains	320	104
Gross Unrealized Losses	(178)	0
Investment securities available for sale, fair value	40,067	15,104
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	(3,302)	(1)
Investment securities available for sale, fair value	$ 19,212	$ 24,270

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=51813488&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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-Section 50
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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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.

+ References

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section S99
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