Fair Value Measurements (Assets and Liabilities Reported on Consolidated Statements of Financial Condition at Fair Values) (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Securities available for sale:
Securities available for sale, at fair value	$ 1,032,235	$ 964,534
Derivative liabilities	20,400
Measured on a non-recurring basis:
Foreclosed assets	10,087	10,546
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Securities available for sale:
Securities available for sale, at fair value	77,969	90,853
Derivative assets	0	0
Derivative liabilities	0	0
Significant Other Observable Inputs (Level 2) [Member]
Securities available for sale:
Securities available for sale, at fair value	954,266	873,681
Derivative assets	18,641	6,854
Derivative liabilities	20,216	6,745
Significant Unobservable Inputs (Level 3) [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Derivative assets	0	0
Derivative liabilities	0	0
US Treasury Obligations [Member]
Securities available for sale:
Securities available for sale, at fair value	8,031	8,004
US Treasury Obligations [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Securities available for sale:
Securities available for sale, at fair value	8,031	8,004
US Treasury Obligations [Member] | Significant Other Observable Inputs (Level 2) [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
US Treasury Obligations [Member] | Significant Unobservable Inputs (Level 3) [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Agency Obligations [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Securities available for sale:
Securities available for sale, at fair value	69,390	82,330
Agency Obligations [Member] | Significant Other Observable Inputs (Level 2) [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Agency Obligations [Member] | Significant Unobservable Inputs (Level 3) [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Mortgage-Backed Securities [Member]
Securities available for sale:
Securities available for sale, at fair value	935,781	863,861
Mortgage-Backed Securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Mortgage-Backed Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Securities available for sale:
Securities available for sale, at fair value	935,781	863,861
Mortgage-Backed Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
State And Municipal Obligations [Member]
Securities available for sale:
Securities available for sale, at fair value	4,353	4,308
State And Municipal Obligations [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
State And Municipal Obligations [Member] | Significant Other Observable Inputs (Level 2) [Member]
Securities available for sale:
Securities available for sale, at fair value	4,353	4,308
State And Municipal Obligations [Member] | Significant Unobservable Inputs (Level 3) [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Corporate Obligations [Member]
Securities available for sale:
Securities available for sale, at fair value	14,132	5,512
Corporate Obligations [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Corporate Obligations [Member] | Significant Other Observable Inputs (Level 2) [Member]
Securities available for sale:
Securities available for sale, at fair value	14,132	5,512
Corporate Obligations [Member] | Significant Unobservable Inputs (Level 3) [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Equity Securities [Member]
Securities available for sale:
Securities available for sale, at fair value	548	519
Equity Securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Securities available for sale:
Securities available for sale, at fair value	548	519
Equity Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Equity Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Measured on a Recurring Basis [Member]
Securities available for sale:
Securities available for sale, at fair value	1,032,235	964,534
Derivative assets	18,641	6,854
Total assets at fair value	1,050,876	971,388
Derivative liabilities	20,216	6,745
Measured on a Recurring Basis [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Securities available for sale:
Securities available for sale, at fair value	77,969	90,853
Derivative assets	0	0
Total assets at fair value	77,969	90,853
Derivative liabilities	0	0
Measured on a Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member]
Securities available for sale:
Securities available for sale, at fair value	954,266	873,681
Derivative assets	18,641	6,854
Total assets at fair value	972,907	880,535
Derivative liabilities	20,216	6,745
Measured on a Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Derivative assets	0	0
Total assets at fair value	0	0
Derivative liabilities	0	0
Measured on a Recurring Basis [Member] | US Treasury Obligations [Member]
Securities available for sale:
Securities available for sale, at fair value	8,031	8,004
Measured on a Recurring Basis [Member] | US Treasury Obligations [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Securities available for sale:
Securities available for sale, at fair value	8,031	8,004
Measured on a Recurring Basis [Member] | US Treasury Obligations [Member] | Significant Other Observable Inputs (Level 2) [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Measured on a Recurring Basis [Member] | US Treasury Obligations [Member] | Significant Unobservable Inputs (Level 3) [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Measured on a Recurring Basis [Member] | Agency Obligations [Member]
Securities available for sale:
Securities available for sale, at fair value	69,390	82,330
Measured on a Recurring Basis [Member] | Agency Obligations [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Securities available for sale:
Securities available for sale, at fair value	69,390	82,330
Measured on a Recurring Basis [Member] | Agency Obligations [Member] | Significant Other Observable Inputs (Level 2) [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Measured on a Recurring Basis [Member] | Agency Obligations [Member] | Significant Unobservable Inputs (Level 3) [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Measured on a Recurring Basis [Member] | Mortgage-Backed Securities [Member]
Securities available for sale:
Securities available for sale, at fair value	935,781	863,861
Measured on a Recurring Basis [Member] | Mortgage-Backed Securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Measured on a Recurring Basis [Member] | Mortgage-Backed Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Securities available for sale:
Securities available for sale, at fair value	935,781	863,861
Measured on a Recurring Basis [Member] | Mortgage-Backed Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Measured on a Recurring Basis [Member] | State And Municipal Obligations [Member]
Securities available for sale:
Securities available for sale, at fair value	4,353	4,308
Measured on a Recurring Basis [Member] | State And Municipal Obligations [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Measured on a Recurring Basis [Member] | State And Municipal Obligations [Member] | Significant Other Observable Inputs (Level 2) [Member]
Securities available for sale:
Securities available for sale, at fair value	4,353	4,308
Measured on a Recurring Basis [Member] | State And Municipal Obligations [Member] | Significant Unobservable Inputs (Level 3) [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Measured on a Recurring Basis [Member] | Corporate Obligations [Member]
Securities available for sale:
Securities available for sale, at fair value	14,132	5,512
Measured on a Recurring Basis [Member] | Corporate Obligations [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Measured on a Recurring Basis [Member] | Corporate Obligations [Member] | Significant Other Observable Inputs (Level 2) [Member]
Securities available for sale:
Securities available for sale, at fair value	14,132	5,512
Measured on a Recurring Basis [Member] | Corporate Obligations [Member] | Significant Unobservable Inputs (Level 3) [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Measured on a Recurring Basis [Member] | Equity Securities [Member]
Securities available for sale:
Securities available for sale, at fair value	548	519
Measured on a Recurring Basis [Member] | Equity Securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Securities available for sale:
Securities available for sale, at fair value	548	519
Measured on a Recurring Basis [Member] | Equity Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
Measured on a Recurring Basis [Member] | Equity Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Securities available for sale:
Securities available for sale, at fair value	0	0
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	9,100	9,481
Foreclosed assets		10,546
Fair value, Measured on a non-recurring basis	19,187	20,027
Measured on a Non-Recurring Basis [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [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
Measured on a Non-Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [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
Measured on a Non-Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member]
Measured on a non-recurring basis:
Loans measured for impairment based on the fair value of the underlying collateral	9,100	9,481
Foreclosed assets	10,087	10,546
Fair value, Measured on a non-recurring basis	$ 19,187	$ 20,027