Fair Value Measurement - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
ASSETS
Total securities available-for-sale	$ 677,221	$ 660,963
US Treasury Securities
ASSETS
Total securities available-for-sale	15,067	14,941
Obligations of U.S. Government Corporations and Agencies
ASSETS
Total securities available-for-sale	271,540	263,303
Collateralized Mortgage Obligations of U.S. Government Corporations and Agencies
ASSETS
Total securities available-for-sale	137,330	128,835
Residential Mortgage-Backed Securities of U.S. Government Corporations and Agencies
ASSETS
Total securities available-for-sale	39,285	40,125
Commercial Mortgage-Backed Securities of U.S. Government Corporations and Agencies
ASSETS
Total securities available-for-sale	70,664	69,204
Obligations of States and Political Subdivisions
ASSETS
Total securities available-for-sale	134,382	134,886
Marketable Equity Securities
ASSETS
Total securities available-for-sale	8,953	9,669
Fair Value Measurements, Recurring
ASSETS
Total securities available-for-sale	677,221	660,963
Trading securities held in a Rabbi Trust	4,069	4,021
Total securities	681,290	664,984
Total Assets	697,097	676,540
LIABILITIES
Total Liabilities	15,237	11,281
Fair Value Measurements, Recurring \| Interest Rate Swaps
ASSETS
Derivative financial assets	15,281	11,295
LIABILITIES
Derivative financial liabilities	15,165	11,276
Fair Value Measurements, Recurring \| Interest Rate Lock Commitments
ASSETS
Derivative financial assets	526	261
Fair Value Measurements, Recurring \| Forward Sale Contracts
LIABILITIES
Derivative financial liabilities	72	5
Fair Value Measurements, Recurring \| US Treasury Securities
ASSETS
Total securities available-for-sale	15,067	14,941
Fair Value Measurements, Recurring \| Obligations of U.S. Government Corporations and Agencies
ASSETS
Total securities available-for-sale	271,540	263,303
Fair Value Measurements, Recurring \| Collateralized Mortgage Obligations of U.S. Government Corporations and Agencies
ASSETS
Total securities available-for-sale	137,330	128,835
Fair Value Measurements, Recurring \| Residential Mortgage-Backed Securities of U.S. Government Corporations and Agencies
ASSETS
Total securities available-for-sale	39,285	40,125
Fair Value Measurements, Recurring \| Commercial Mortgage-Backed Securities of U.S. Government Corporations and Agencies
ASSETS
Total securities available-for-sale	70,664	69,204
Fair Value Measurements, Recurring \| Obligations of States and Political Subdivisions
ASSETS
Total securities available-for-sale	134,382	134,886
Fair Value Measurements, Recurring \| Marketable Equity Securities
ASSETS
Total securities available-for-sale	8,953	9,669
Fair Value Measurements, Recurring \| Level 1
ASSETS
Total securities available-for-sale	0	0
Trading securities held in a Rabbi Trust	4,069	4,021
Total securities	4,069	4,021
Total Assets	4,069	4,021
LIABILITIES
Total Liabilities	0	0
Fair Value Measurements, Recurring \| Level 1 \| Interest Rate Swaps
ASSETS
Derivative financial assets		0
LIABILITIES
Derivative financial liabilities		0
Fair Value Measurements, Recurring \| Level 1 \| Interest Rate Lock Commitments
ASSETS
Derivative financial assets		0
Fair Value Measurements, Recurring \| Level 1 \| Forward Sale Contracts
LIABILITIES
Derivative financial liabilities		0
Fair Value Measurements, Recurring \| Level 1 \| US Treasury Securities
ASSETS
Total securities available-for-sale		0
Fair Value Measurements, Recurring \| Level 1 \| Obligations of U.S. Government Corporations and Agencies
ASSETS
Total securities available-for-sale		0
Fair Value Measurements, Recurring \| Level 1 \| Collateralized Mortgage Obligations of U.S. Government Corporations and Agencies
ASSETS
Total securities available-for-sale		0
Fair Value Measurements, Recurring \| Level 1 \| Residential Mortgage-Backed Securities of U.S. Government Corporations and Agencies
ASSETS
Total securities available-for-sale		0
Fair Value Measurements, Recurring \| Level 1 \| Commercial Mortgage-Backed Securities of U.S. Government Corporations and Agencies
ASSETS
Total securities available-for-sale		0
Fair Value Measurements, Recurring \| Level 1 \| Obligations of States and Political Subdivisions
ASSETS
Total securities available-for-sale		0
Fair Value Measurements, Recurring \| Level 1 \| Marketable Equity Securities
ASSETS
Total securities available-for-sale	0	0
Fair Value Measurements, Recurring \| Level 2
ASSETS
Total securities available-for-sale	677,221	660,963
Trading securities held in a Rabbi Trust		0
Total securities	677,221	660,963
Total Assets	693,028	672,519
LIABILITIES
Total Liabilities	15,237	11,281
Fair Value Measurements, Recurring \| Level 2 \| Interest Rate Swaps
ASSETS
Derivative financial assets	15,281	11,295
LIABILITIES
Derivative financial liabilities	15,165	11,276
Fair Value Measurements, Recurring \| Level 2 \| Interest Rate Lock Commitments
ASSETS
Derivative financial assets	526	261
Fair Value Measurements, Recurring \| Level 2 \| Forward Sale Contracts
LIABILITIES
Derivative financial liabilities	72	5
Fair Value Measurements, Recurring \| Level 2 \| US Treasury Securities
ASSETS
Total securities available-for-sale	15,067	14,941
Fair Value Measurements, Recurring \| Level 2 \| Obligations of U.S. Government Corporations and Agencies
ASSETS
Total securities available-for-sale	271,540	263,303
Fair Value Measurements, Recurring \| Level 2 \| Collateralized Mortgage Obligations of U.S. Government Corporations and Agencies
ASSETS
Total securities available-for-sale	137,330	128,835
Fair Value Measurements, Recurring \| Level 2 \| Residential Mortgage-Backed Securities of U.S. Government Corporations and Agencies
ASSETS
Total securities available-for-sale	39,285	40,125
Fair Value Measurements, Recurring \| Level 2 \| Commercial Mortgage-Backed Securities of U.S. Government Corporations and Agencies
ASSETS
Total securities available-for-sale	70,664	69,204
Fair Value Measurements, Recurring \| Level 2 \| Obligations of States and Political Subdivisions
ASSETS
Total securities available-for-sale	134,382	134,886
Fair Value Measurements, Recurring \| Level 2 \| Marketable Equity Securities
ASSETS
Total securities available-for-sale	8,953	9,669
Fair Value Measurements, Recurring \| Level 3
ASSETS
Total securities available-for-sale		0
Trading securities held in a Rabbi Trust		0
Total securities		0
Total Assets		0
LIABILITIES
Total Liabilities	$ 0	0
Fair Value Measurements, Recurring \| Level 3 \| Interest Rate Swaps
ASSETS
Derivative financial assets		0
LIABILITIES
Derivative financial liabilities		0
Fair Value Measurements, Recurring \| Level 3 \| Interest Rate Lock Commitments
ASSETS
Derivative financial assets		0
Fair Value Measurements, Recurring \| Level 3 \| Forward Sale Contracts
LIABILITIES
Derivative financial liabilities		0
Fair Value Measurements, Recurring \| Level 3 \| US Treasury Securities
ASSETS
Total securities available-for-sale		0
Fair Value Measurements, Recurring \| Level 3 \| Obligations of U.S. Government Corporations and Agencies
ASSETS
Total securities available-for-sale		0
Fair Value Measurements, Recurring \| Level 3 \| Collateralized Mortgage Obligations of U.S. Government Corporations and Agencies
ASSETS
Total securities available-for-sale		0
Fair Value Measurements, Recurring \| Level 3 \| Residential Mortgage-Backed Securities of U.S. Government Corporations and Agencies
ASSETS
Total securities available-for-sale		0
Fair Value Measurements, Recurring \| Level 3 \| Commercial Mortgage-Backed Securities of U.S. Government Corporations and Agencies
ASSETS
Total securities available-for-sale		0
Fair Value Measurements, Recurring \| Level 3 \| Obligations of States and Political Subdivisions
ASSETS
Total securities available-for-sale		0
Fair Value Measurements, Recurring \| Level 3 \| Marketable Equity Securities
ASSETS
Total securities available-for-sale		$ 0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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=66048111&loc=d3e19207-110258

+ Details

Name:	us-gaap_AssetsFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ 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=65884222&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66010992&loc=d3e26610-111562

+ Details

Name:	us-gaap_AvailableForSaleSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41271-113958

Reference 3: 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=73719730&loc=d3e13433-108611

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13495-108611

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=51825145&loc=SL20226008-175313

+ Details

Name:	us-gaap_DerivativeAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=51825145&loc=SL20226008-175313

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13495-108611

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 4: 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=73719730&loc=d3e13433-108611

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41271-113958

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958

+ Details

Name:	us-gaap_DerivativeLiabilities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

Name:	us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ 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 FASB
-Name Accounting Standards Codification
-Glossary Trading Securities
-URI http://asc.fasb.org/extlink&oid=6526789

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(5))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(6))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 35
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=27723805&loc=d3e24584-111560

Reference 6: 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(2))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=65884222&loc=d3e22054-111558

Reference 8: 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(a)(1))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 9: 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

+ Details

Name:	us-gaap_InvestmentsFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value of financial and nonfinancial obligations.

+ References

+ Details

Name:	us-gaap_LiabilitiesFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of investments in debt and equity securities and other forms of securities that provide ownership interests classified as trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=66010992&loc=d3e26626-111562

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.4)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66010992&loc=d3e26610-111562

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Trading Securities
-URI http://asc.fasb.org/extlink&oid=6526789

+ Details

Name:	us-gaap_TradingSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_USTreasurySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_USGovernmentCorporationsAndAgenciesSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_CollateralizedMortgageObligationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_ResidentialMortgageBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_CommercialMortgageBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_USStatesAndPoliticalSubdivisionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_EquitySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_InterestRateSwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_InterestRateLockCommitmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_ForwardContractsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: