Fair Value Measurements - Assets and Liabilities Reported on Consolidated Statements of Financial Condition at Fair Values (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Securities available for sale:
Securities available for sale, at fair value	$ 1,156,986	$ 1,157,594
Measured on a non-recurring basis:
Foreclosed assets	6,983	5,486
Measured on a Recurring Basis [Member]
Securities available for sale:
Securities available for sale, at fair value	1,156,986	1,157,594
Measured on a Non-Recurring Basis [Member]
Measured on a non-recurring basis:
Loans measured for impairment based on the fair value of the underlying collateral	27,548	29,782
Foreclosed assets	6,983	5,486
Fair value, Measured on a non-recurring basis	34,531	35,268
Agency Obligations [Member] | Measured on a Recurring Basis [Member]
Securities available for sale:
Securities available for sale, at fair value	91,208	93,416
Mortgage-Backed Securities [Member]
Securities available for sale:
Securities available for sale, at fair value	1,048,024	1,054,974
Mortgage-Backed Securities [Member] | Measured on a Recurring Basis [Member]
Securities available for sale:
Securities available for sale, at fair value	1,048,024	1,054,974
State and Municipal Obligations [Member]
Securities available for sale:
Securities available for sale, at fair value	7,699	8,758
State and Municipal Obligations [Member] | Measured on a Recurring Basis [Member]
Securities available for sale:
Securities available for sale, at fair value	7,699	8,758
Corporate Obligations [Member] | Measured on a Recurring Basis [Member]
Securities available for sale:
Securities available for sale, at fair value	9,539
Equity Securities [Member]
Securities available for sale:
Securities available for sale, at fair value	516	446
Equity Securities [Member] | Measured on a Recurring Basis [Member]
Securities available for sale:
Securities available for sale, at fair value	516	446
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Securities available for sale:
Securities available for sale, at fair value	91,724	93,862
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Measured on a Recurring Basis [Member]
Securities available for sale:
Securities available for sale, at fair value	91,724	93,862
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Measured on a Non-Recurring Basis [Member]
Measured on a non-recurring basis:
Loans measured for impairment based on the fair value of the underlying collateral	0	0
Foreclosed assets	0	0
Fair value, Measured on a non-recurring basis	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Agency Obligations [Member]
Securities available for sale:
Securities available for sale, at fair value	91,208	93,416
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Agency Obligations [Member] | Measured on a Recurring Basis [Member]
Securities available for sale:
Securities available for sale, at fair value	91,208	93,416
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Mortgage-Backed Securities [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Mortgage-Backed Securities [Member] | Measured on a Recurring Basis [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | State and Municipal Obligations [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | State and Municipal Obligations [Member] | Measured on a Recurring Basis [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Corporate Obligations [Member]
Securities available for sale:
Securities available for sale, at fair value	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Corporate Obligations [Member] | Measured on a Recurring Basis [Member]
Securities available for sale:
Securities available for sale, at fair value	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Equity Securities [Member]
Securities available for sale:
Securities available for sale, at fair value	516	446
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Equity Securities [Member] | Measured on a Recurring Basis [Member]
Securities available for sale:
Securities available for sale, at fair value	516	446
Significant Other Observable Inputs (Level 2) [Member]
Securities available for sale:
Securities available for sale, at fair value	1,065,262	1,063,732
Significant Other Observable Inputs (Level 2) [Member] | Measured on a Recurring Basis [Member]
Securities available for sale:
Securities available for sale, at fair value	1,065,262	1,063,732
Significant Other Observable Inputs (Level 2) [Member] | Measured on a Non-Recurring Basis [Member]
Measured on a non-recurring basis:
Loans measured for impairment based on the fair value of the underlying collateral	0	0
Foreclosed assets	0	0
Fair value, Measured on a non-recurring basis	0	0
Significant Other Observable Inputs (Level 2) [Member] | Agency Obligations [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Significant Other Observable Inputs (Level 2) [Member] | Agency Obligations [Member] | Measured on a Recurring Basis [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Significant Other Observable Inputs (Level 2) [Member] | Mortgage-Backed Securities [Member]
Securities available for sale:
Securities available for sale, at fair value	1,048,024	1,054,974
Significant Other Observable Inputs (Level 2) [Member] | Mortgage-Backed Securities [Member] | Measured on a Recurring Basis [Member]
Securities available for sale:
Securities available for sale, at fair value	1,048,024	1,054,974
Significant Other Observable Inputs (Level 2) [Member] | State and Municipal Obligations [Member]
Securities available for sale:
Securities available for sale, at fair value	7,699	8,758
Significant Other Observable Inputs (Level 2) [Member] | State and Municipal Obligations [Member] | Measured on a Recurring Basis [Member]
Securities available for sale:
Securities available for sale, at fair value	7,699	8,758
Significant Other Observable Inputs (Level 2) [Member] | Corporate Obligations [Member]
Securities available for sale:
Securities available for sale, at fair value	9,539
Significant Other Observable Inputs (Level 2) [Member] | Corporate Obligations [Member] | Measured on a Recurring Basis [Member]
Securities available for sale:
Securities available for sale, at fair value	9,539
Significant Other Observable Inputs (Level 2) [Member] | Equity Securities [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Significant Other Observable Inputs (Level 2) [Member] | Equity Securities [Member] | Measured on a Recurring Basis [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Significant Unobservable Inputs (Level 3) [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Significant Unobservable Inputs (Level 3) [Member] | Measured on a Recurring Basis [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Significant Unobservable Inputs (Level 3) [Member] | Measured on a Non-Recurring Basis [Member]
Measured on a non-recurring basis:
Loans measured for impairment based on the fair value of the underlying collateral	27,548	29,782
Foreclosed assets	6,983	5,486
Fair value, Measured on a non-recurring basis	34,531	35,268
Significant Unobservable Inputs (Level 3) [Member] | Agency Obligations [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Significant Unobservable Inputs (Level 3) [Member] | Agency Obligations [Member] | Measured on a Recurring Basis [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Significant Unobservable Inputs (Level 3) [Member] | Mortgage-Backed Securities [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Significant Unobservable Inputs (Level 3) [Member] | Mortgage-Backed Securities [Member] | Measured on a Recurring Basis [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Significant Unobservable Inputs (Level 3) [Member] | State and Municipal Obligations [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Significant Unobservable Inputs (Level 3) [Member] | State and Municipal Obligations [Member] | Measured on a Recurring Basis [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Significant Unobservable Inputs (Level 3) [Member] | Corporate Obligations [Member]
Securities available for sale:
Securities available for sale, at fair value	0
Significant Unobservable Inputs (Level 3) [Member] | Corporate Obligations [Member] | Measured on a Recurring Basis [Member]
Securities available for sale:
Securities available for sale, at fair value	0
Significant Unobservable Inputs (Level 3) [Member] | Equity Securities [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Significant Unobservable Inputs (Level 3) [Member] | Equity Securities [Member] | Measured on a Recurring Basis [Member]
Securities available for sale:
Securities available for sale, at fair value	$ 0	$ 0