Investment Securities - Schedule of Securities in Other Assets on Company's Consolidated Balance Sheets (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Investments, Debt and Equity Securities [Abstract]
Federal Home Loan Bank (FHLB) stock	$ 38,476us-gaap_FederalHomeLoanBankStock	$ 24,369us-gaap_FederalHomeLoanBankStock
Federal Reserve Bank (FRB) stock	34,348us-gaap_FederalReserveBankStock	28,098us-gaap_FederalReserveBankStock
Other investments	1,306us-gaap_OtherInvestments	1,306us-gaap_OtherInvestments
Total	$ 74,130	$ 53,773

Federal Home Loan Bank (FHLB) stock represents an equity interest in a FHLB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity).

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 325

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6478792&loc=d3e63345-112809

+ Details

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- Definition

Federal Reserve Bank stock represents an equity interest in the Federal Reserve Bank. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity).

+ References

+ Details

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- Details

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- Definition

For an unclassified balance sheet, this item represents investments in common and preferred stocks and other forms of securities that provide ownership interests in a corporation.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 1

-Subparagraph b

-Article 7

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.1(b))

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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- Definition

Other investments not otherwise specified in the taxonomy.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.12)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 12

-Article 5

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 1

-Subparagraph g

-Article 7

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.1(f,g))

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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