Fair Values of Assets and Liabilities - Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Debt Securities	$ 1,169,328	$ 1,140,916
Fair Value of Investment Securities	1,171,303	1,142,776
Other investments	28,228	39,796
Loans Held for Sale	0	13,412
Other Assets	16,480	16,064
Total Assets	1,216,011	1,212,048
Other Liabilities	18,726	18,986
Total Liabilities	18,726	18,986
Equities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value of Investment Securities	1,975	1,860
US Government Agencies Debt Securities [Member] \| Mortgage-Backed Securities-Residential [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Debt Securities	31,664	36,194
Obligations of U.S. Government-Sponsored Enterprises [Member] \| Mortgage-Backed Securities-Residential [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Debt Securities	864,401	801,031
Obligations of U.S. Government-Sponsored Enterprises [Member] \| Mortgage-Backed Securities-Commercial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Debt Securities	149	193
Obligations of U.S. Government-Sponsored Enterprises [Member] \| Other Government - Sponsored Enterprises [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Debt Securities	242,664	268,648
Obligations of States and Political Subdivisions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Debt Securities	86	459
Corporate Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Debt Securities	6,991	11,411
Fair Value of Investment Securities	7,000	11,400
Pooled Trust Preferred Collateralized Debt Obligations [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Debt Securities	23,373	22,980
Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Debt Securities	0	0
Fair Value of Investment Securities	555	440
Other investments	0	0
Loans Held for Sale	0	0
Other Assets	0	0
Total Assets	555	440
Other Liabilities	0	0
Total Liabilities	0	0
Level 1 [Member] \| Equities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value of Investment Securities	555	440
Level 1 [Member] \| US Government Agencies Debt Securities [Member] \| Mortgage-Backed Securities-Residential [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Debt Securities	0	0
Level 1 [Member] \| Obligations of U.S. Government-Sponsored Enterprises [Member] \| Mortgage-Backed Securities-Residential [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Debt Securities	0	0
Level 1 [Member] \| Obligations of U.S. Government-Sponsored Enterprises [Member] \| Mortgage-Backed Securities-Commercial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Debt Securities	0	0
Level 1 [Member] \| Obligations of U.S. Government-Sponsored Enterprises [Member] \| Other Government - Sponsored Enterprises [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Debt Securities	0	0
Level 1 [Member] \| Obligations of States and Political Subdivisions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Debt Securities	0	0
Level 1 [Member] \| Corporate Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Debt Securities	0	0
Level 1 [Member] \| Pooled Trust Preferred Collateralized Debt Obligations [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Debt Securities	0	0
Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Debt Securities	1,145,955	1,117,936
Fair Value of Investment Securities	1,145,955	1,117,936
Other investments	28,228	39,796
Loans Held for Sale	0	0
Other Assets	16,480	16,064
Total Assets	1,190,663	1,173,796
Other Liabilities	18,726	18,986
Total Liabilities	18,726	18,986
Level 2 [Member] \| Equities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value of Investment Securities	0	0
Level 2 [Member] \| US Government Agencies Debt Securities [Member] \| Mortgage-Backed Securities-Residential [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Debt Securities	31,664	36,194
Level 2 [Member] \| Obligations of U.S. Government-Sponsored Enterprises [Member] \| Mortgage-Backed Securities-Residential [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Debt Securities	864,401	801,031
Level 2 [Member] \| Obligations of U.S. Government-Sponsored Enterprises [Member] \| Mortgage-Backed Securities-Commercial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Debt Securities	149	193
Level 2 [Member] \| Obligations of U.S. Government-Sponsored Enterprises [Member] \| Other Government - Sponsored Enterprises [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Debt Securities	242,664	268,648
Level 2 [Member] \| Obligations of States and Political Subdivisions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Debt Securities	86	459
Level 2 [Member] \| Corporate Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Debt Securities	6,991	11,411
Level 2 [Member] \| Pooled Trust Preferred Collateralized Debt Obligations [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Debt Securities	0	0
Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Debt Securities	23,373	22,980
Fair Value of Investment Securities	24,793	24,400
Other investments	0	0
Loans Held for Sale	0	13,412
Other Assets	0	0
Total Assets	24,793	37,812
Other Liabilities	0	0
Total Liabilities	0	0
Level 3 [Member] \| Equities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value of Investment Securities	1,420	1,420
Level 3 [Member] \| US Government Agencies Debt Securities [Member] \| Mortgage-Backed Securities-Residential [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Debt Securities	0	0
Level 3 [Member] \| Obligations of U.S. Government-Sponsored Enterprises [Member] \| Mortgage-Backed Securities-Residential [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Debt Securities	0	0
Level 3 [Member] \| Obligations of U.S. Government-Sponsored Enterprises [Member] \| Mortgage-Backed Securities-Commercial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Debt Securities	0	0
Level 3 [Member] \| Obligations of U.S. Government-Sponsored Enterprises [Member] \| Other Government - Sponsored Enterprises [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Debt Securities	0	0
Level 3 [Member] \| Obligations of States and Political Subdivisions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Debt Securities	0	0
Level 3 [Member] \| Corporate Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Debt Securities	0	0
Level 3 [Member] \| Pooled Trust Preferred Collateralized Debt Obligations [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Debt Securities	$ 23,373	$ 22,980

This element represents the aggregate of the assets reported on the balance sheet at period end measured at fair value by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258

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- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

+ References

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=7534914&loc=d3e22054-111558

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 12

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Available-for-Sale Securities

-URI http://asc.fasb.org/extlink&oid=6505594

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 10

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13433-108611

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 12

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- Definition

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).

+ References

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

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

-Publisher AICPA

-Name Audit and Accounting Guide (AAG)

-Number AAG-DEP

-Paragraph 26

-IssueDate 2006-05-01

-Chapter 12

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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- Definition

This element represents the aggregate of the liabilities reported on the balance sheet at period end measured at fair value by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements.

+ References

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