Investment Securities - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Held-to-maturity Securities Pledged as Collateral	$ 217,800		$ 119,200
Proceeds from Sale of Available-for-sale Securities	0	$ 0
Available-for-sale securities pledged as collateral	$ 438,400		$ 445,800

The fair value of available-for-sale securities that serve as collateral for borrowings.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5086-111524

+ Details

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Period Type:	instant

- Definition

The carrying amount of held-to-maturity securities that serve as collateral for borrowings.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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- References

No definition available.

+ Details

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- Definition

The cash inflow associated with the sale of debt and equity securities classified as available-for-sale securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Investing Activities
-URI http://asc.fasb.org/extlink&oid=6516133

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=66010992&loc=d3e26853-111562

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (a),(b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3179-108585

+ Details

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