Investment Securities - Amortized Cost and 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	$ 345,342	$ 297,001
Gross Unrealized Gains	358	840
Gross Unrealized (Losses)	(4,177)	(3,242)
Fair Value	341,523	294,599
Held-to-maturity Securities, Fair Value	15,422	0
U.S. government sponsored and federal agency obligations
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,130	3,245
Gross Unrealized Gains	6	16
Gross Unrealized (Losses)	0	0
Fair Value	3,136	3,261
Mortgage backed securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	342,211	293,755
Gross Unrealized Gains	350	822
Gross Unrealized (Losses)	(4,177)	(3,242)
Fair Value	338,384	291,335
Other securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1	1
Gross Unrealized Gains	2	2
Gross Unrealized (Losses)	0	0
Fair Value	3	$ 3
Corporate Bond Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	15,492
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	0
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	(70)
Held-to-maturity Securities, Fair Value	$ 15,422

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

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

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-Publisher FASB
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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 of investments in debt securities classified as available-for-sale, expected to be converted to cash, sold or exchanged within one year or the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Amount of accumulated unrealized gain on investments in debt securities classified as held-to-maturity.

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Amount of accumulated unrealized loss on investments in debt securities classified as held-to-maturity.

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Amount before other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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Fair value of investments in debt securities classified as held-to-maturity.

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