Fair Value Measurement - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale securities, Fair value	$ 507,125	$ 511,006
Fair Value, Measurements, Recurring [Member] | Interest Rate Caps [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale securities, Fair value	268	546
Fair Value, Measurements, Recurring [Member] | US Treasury and Government Sponsored Entities Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale securities, Fair value	231,639	222,293
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale securities, Fair value		445
Fair Value, Measurements, Recurring [Member] | Mortgage-Backed GSE Securities: Residential [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale securities, Fair value	275,486	288,268
Fair Value, Measurements, Recurring [Member] | Purchased Certificate of Deposit Option [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale securities, Fair value	557	155
Fair Value, Measurements, Recurring [Member] | Written Certificate of Deposit Option [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale securities, Fair value	557	155
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Equity Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale securities, Fair value		445
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | US Treasury and Government Sponsored Entities Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale securities, Fair value	231,639	222,293
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Mortgage-Backed GSE Securities: Residential [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale securities, Fair value	275,486	288,268
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Purchased Certificate of Deposit Option [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale securities, Fair value	557	155
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Written Certificate of Deposit Option [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale securities, Fair value	557	155
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Interest Rate Caps [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale securities, Fair value	$ 268	$ 546