Fair Value Measurements (Assets and Liabilities Reported on Consolidated Statements of Financial Condition at Fair Values) (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Securities available for sale:
Securities available for sale, at fair value	$ 1,048,119	$ 1,040,386
Derivative liabilities	746
Measured on a non-recurring basis:
Foreclosed assets	7,684	7,991
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Securities available for sale:
Securities available for sale, at fair value	57,662	65,745
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	990,457	974,641
Derivative assets	7,429	7,441
Derivative liabilities	6,872	6,750
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	7,996	8,008
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	7,996	8,008
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	49,108	57,188
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	967,318	951,861
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	967,318	951,861
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	3,791	3,743
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	3,791	3,743
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	19,348	19,037
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	19,348	19,037
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	558	549
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	558	549
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	1,048,119	1,040,386
Derivative assets	7,429	7,441
Total assets at fair value	1,055,548	1,047,827
Derivative liabilities	6,872	6,750
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	57,662	65,745
Derivative assets	0	0
Total assets at fair value	57,662	65,745
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	990,457	974,641
Derivative assets	7,429	7,441
Total assets at fair value	997,886	982,082
Derivative liabilities	6,872	6,750
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	7,996	8,008
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	7,996	8,008
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	49,108	57,188
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	49,108	57,188
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	967,318	951,861
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	967,318	951,861
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	3,791	3,743
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	3,791	3,743
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	19,348	19,037
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	19,348	19,037
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	558	549
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	558	549
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	13,082	11,001
Foreclosed assets	7,684	7,991
Fair value, Measured on a non-recurring basis	20,766	18,992
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	13,082	11,001
Foreclosed assets	7,684	7,991
Fair value, Measured on a non-recurring basis	$ 20,766	$ 18,992