Fair Value Measurement - Assets Measured on Non-recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Mortgage servicing assets	$ 387	$ 4,920
Permanent Real Estate Loans [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Impaired loans	637	6,166
Construction Loans [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Impaired loans	1,564	3,489
Permanent Real Estate [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Other real estate owned, net:	2,315	3,172
Construction [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Other real estate owned, net:	4,125	6,918
Commercial Loans [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Impaired loans		257
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Mortgage servicing assets
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Permanent Real Estate Loans [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Impaired loans
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Construction Loans [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Impaired loans
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Permanent Real Estate [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Other real estate owned, net:
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Construction [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Other real estate owned, net:
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Commercial Loans [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Impaired loans
Significant Other Observable Inputs (Level 2) [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Mortgage servicing assets	387	4,920
Significant Other Observable Inputs (Level 2) [Member] | Permanent Real Estate Loans [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Impaired loans
Significant Other Observable Inputs (Level 2) [Member] | Construction Loans [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Impaired loans
Significant Other Observable Inputs (Level 2) [Member] | Permanent Real Estate [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Other real estate owned, net:
Significant Other Observable Inputs (Level 2) [Member] | Construction [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Other real estate owned, net:
Significant Other Observable Inputs (Level 2) [Member] | Commercial Loans [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Impaired loans
Significant Unobservable Inputs (Level 3) [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Mortgage servicing assets
Significant Unobservable Inputs (Level 3) [Member] | Permanent Real Estate Loans [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Impaired loans	637	6,166
Significant Unobservable Inputs (Level 3) [Member] | Construction Loans [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Impaired loans	1,564	3,489
Significant Unobservable Inputs (Level 3) [Member] | Permanent Real Estate [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Other real estate owned, net:	2,315	3,172
Significant Unobservable Inputs (Level 3) [Member] | Construction [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Other real estate owned, net:	4,125	6,918
Significant Unobservable Inputs (Level 3) [Member] | Commercial Loans [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Impaired loans		$ 257