Fair Value Measurements (Assets and Liabilities Reported on Consolidated Statements of Financial Condition at Fair Values) (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Securities available for sale:
Securities available for sale, at fair value	$ 1,038,968	$ 1,040,386
Derivative liabilities	2,300
Measured on a non-recurring basis:
Foreclosed assets	6,603	7,991
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Securities available for sale:
Securities available for sale, at fair value	48,613	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	990,355	974,641
Derivative assets	7,946	7,441
Derivative liabilities	7,560	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	5,988	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	5,988	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	42,049	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	965,096	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	965,096	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	3,821	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	3,821	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	21,438	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	21,438	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	576	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	576	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	1,038,968	1,040,386
Derivative assets	7,946	7,441
Total assets at fair value	1,046,914	1,047,827
Derivative liabilities	7,560	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	48,613	65,745
Derivative assets	0	0
Total assets at fair value	48,613	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	990,355	974,641
Derivative assets	7,946	7,441
Total assets at fair value	998,301	982,082
Derivative liabilities	7,560	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	5,988	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	5,988	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	42,049	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	42,049	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	965,096	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	965,096	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	3,821	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	3,821	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	21,438	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	21,438	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	576	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	576	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	6,890	11,001
Fair value, Measured on a non-recurring basis	13,493	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	6,890	11,001
Foreclosed assets	6,603	7,991
Fair value, Measured on a non-recurring basis	$ 13,493	$ 18,992