Fair Value - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Securities Available For Sale:
Securities available for sale	$ 587,333	$ 685,720
Trading Securities:
Trading securities	4,489	4,505
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Securities Available For Sale:
Securities available for sale	993	1,002
Trading Securities:
Trading securities	4,279	4,296
Liabilities,
Interest rate swaps	0	0
Significant Other Observable Inputs (Level 2) [Member]
Securities Available For Sale:
Securities available for sale	585,180	683,813
Trading Securities:
Trading securities	210	209
Liabilities,
Interest rate swaps	(908)	(946)
Significant Unobservable Inputs (Level 3) [Member]
Securities Available For Sale:
Securities available for sale	1,160	905
Trading Securities:
Trading securities	0	0
Liabilities,
Interest rate swaps	0	0
Fair Value Measurement on Recurring Basis [Member]
Securities Available For Sale:
Securities available for sale	587,333	685,720
Trading Securities:
Trading securities	4,489	4,505
Liabilities,
Interest rate swaps	(908)	(946)
Fair Value Measurement on Recurring Basis [Member] | U.S. Government Sponsored Entities [Member]
Securities Available For Sale:
Securities available for sale	147,009	155,564
Trading Securities:
Trading securities	55	54
Fair Value Measurement on Recurring Basis [Member] | States and Political Subdivisions [Member]
Securities Available For Sale:
Securities available for sale	180,429	181,002
Fair Value Measurement on Recurring Basis [Member] | Residential and Multi-Family Mortgage [Member]
Securities Available For Sale:
Securities available for sale	184,347	265,164
Fair Value Measurement on Recurring Basis [Member] | Corporate Notes and Bonds [Member]
Securities Available For Sale:
Securities available for sale	19,036	19,430
Trading Securities:
Trading securities	155	157
Fair Value Measurement on Recurring Basis [Member] | Pooled Trust Preferred [Member]
Securities Available For Sale:
Securities available for sale	1,160	905
Fair Value Measurement on Recurring Basis [Member] | Pooled SBA [Member]
Securities Available For Sale:
Securities available for sale	54,359	62,653
Fair Value Measurement on Recurring Basis [Member] | Other Securities [Member]
Securities Available For Sale:
Securities available for sale	993	1,002
Fair Value Measurement on Recurring Basis [Member] | Corporate Equity Securities [Member]
Trading Securities:
Trading securities	2,997	3,044
Fair Value Measurement on Recurring Basis [Member] | Mutual Funds [Member]
Trading Securities:
Trading securities	1,028	997
Fair Value Measurement on Recurring Basis [Member] | Certificates of Deposit [Member]
Trading Securities:
Trading securities	254	253
Fair Value Measurement on Recurring Basis [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Securities Available For Sale:
Securities available for sale	993	1,002
Trading Securities:
Trading securities	4,279	4,294
Liabilities,
Interest rate swaps	0	0
Fair Value Measurement on Recurring Basis [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | U.S. Government Sponsored Entities [Member]
Securities Available For Sale:
Securities available for sale	0	0
Trading Securities:
Trading securities	0	0
Fair Value Measurement on Recurring Basis [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | States and Political Subdivisions [Member]
Securities Available For Sale:
Securities available for sale	0	0
Fair Value Measurement on Recurring Basis [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Residential and Multi-Family Mortgage [Member]
Securities Available For Sale:
Securities available for sale	0	0
Fair Value Measurement on Recurring Basis [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Corporate Notes and Bonds [Member]
Securities Available For Sale:
Securities available for sale	0	0
Trading Securities:
Trading securities	0	0
Fair Value Measurement on Recurring Basis [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pooled Trust Preferred [Member]
Securities Available For Sale:
Securities available for sale	0	0
Fair Value Measurement on Recurring Basis [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pooled SBA [Member]
Securities Available For Sale:
Securities available for sale	0	0
Fair Value Measurement on Recurring Basis [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Securities [Member]
Securities Available For Sale:
Securities available for sale	993	1,002
Fair Value Measurement on Recurring Basis [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Corporate Equity Securities [Member]
Trading Securities:
Trading securities	2,997	3,044
Fair Value Measurement on Recurring Basis [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Mutual Funds [Member]
Trading Securities:
Trading securities	1,028	997
Fair Value Measurement on Recurring Basis [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Certificates of Deposit [Member]
Trading Securities:
Trading securities	254	253
Fair Value Measurement on Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member]
Securities Available For Sale:
Securities available for sale	585,180	683,813
Trading Securities:
Trading securities	210	211
Liabilities,
Interest rate swaps	(908)	(946)
Fair Value Measurement on Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | U.S. Government Sponsored Entities [Member]
Securities Available For Sale:
Securities available for sale	147,009	155,564
Trading Securities:
Trading securities	55	54
Fair Value Measurement on Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | States and Political Subdivisions [Member]
Securities Available For Sale:
Securities available for sale	180,429	181,002
Fair Value Measurement on Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | Residential and Multi-Family Mortgage [Member]
Securities Available For Sale:
Securities available for sale	184,347	265,164
Fair Value Measurement on Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | Corporate Notes and Bonds [Member]
Securities Available For Sale:
Securities available for sale	19,036	19,430
Trading Securities:
Trading securities	155	157
Fair Value Measurement on Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pooled Trust Preferred [Member]
Securities Available For Sale:
Securities available for sale	0	0
Fair Value Measurement on Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pooled SBA [Member]
Securities Available For Sale:
Securities available for sale	54,359	62,653
Fair Value Measurement on Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Securities [Member]
Securities Available For Sale:
Securities available for sale	0	0
Fair Value Measurement on Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | Corporate Equity Securities [Member]
Trading Securities:
Trading securities	0	0
Fair Value Measurement on Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | Mutual Funds [Member]
Trading Securities:
Trading securities	0	0
Fair Value Measurement on Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | Certificates of Deposit [Member]
Trading Securities:
Trading securities	0	0
Fair Value Measurement on Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member]
Securities Available For Sale:
Securities available for sale	1,160	905
Trading Securities:
Trading securities	0	0
Liabilities,
Interest rate swaps	0	0
Fair Value Measurement on Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member] | U.S. Government Sponsored Entities [Member]
Securities Available For Sale:
Securities available for sale	0	0
Trading Securities:
Trading securities	0	0
Fair Value Measurement on Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member] | States and Political Subdivisions [Member]
Securities Available For Sale:
Securities available for sale	0	0
Fair Value Measurement on Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member] | Residential and Multi-Family Mortgage [Member]
Securities Available For Sale:
Securities available for sale	0	0
Fair Value Measurement on Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member] | Corporate Notes and Bonds [Member]
Securities Available For Sale:
Securities available for sale	0	0
Trading Securities:
Trading securities	0	0
Fair Value Measurement on Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pooled Trust Preferred [Member]
Securities Available For Sale:
Securities available for sale	1,160	905
Fair Value Measurement on Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pooled SBA [Member]
Securities Available For Sale:
Securities available for sale	0	0
Fair Value Measurement on Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Securities [Member]
Securities Available For Sale:
Securities available for sale	0	0
Fair Value Measurement on Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member] | Corporate Equity Securities [Member]
Trading Securities:
Trading securities	0
Fair Value Measurement on Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member] | Mutual Funds [Member]
Trading Securities:
Trading securities	0	0
Fair Value Measurement on Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member] | Certificates of Deposit [Member]
Trading Securities:
Trading securities	$ 0	$ 0