Fair Value Measurements (Assets and Liabilities) (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities:	$ 989,833	$ 976,919
Held to maturity debt securities, fair value	459,224	467,966
Equity securities	685	825
Derivative liabilities	127,700
Foreclosed assets	4,219	2,715
Quoted Prices in Active  Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities:	0	0
Held to maturity debt securities, fair value	7,432	6,601
Equity securities	685	825
Derivative assets	0	0
Derivative liabilities	0	0
Significant Other Observable  Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities:	989,833	976,919
Held to maturity debt securities, fair value	451,792	461,365
Equity securities	0	0
Derivative assets	111,608	39,305
Derivative liabilities	120,176	39,356
Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities:	0	0
Held to maturity debt securities, fair value	0	0
Equity securities	0	0
Derivative assets	0	0
Derivative liabilities	0	0
Mortgage-Backed Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities:	960,177	947,430
Held to maturity debt securities, fair value	108	122
Mortgage-Backed Securities | Quoted Prices in Active  Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities:	0	0
Held to maturity debt securities, fair value	0	0
Mortgage-Backed Securities | Significant Other Observable  Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities:	960,177	947,430
Held to maturity debt securities, fair value	108	122
Mortgage-Backed Securities | Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities:	0	0
Held to maturity debt securities, fair value	0	0
State And Municipal Obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities:	4,049	4,079
Held to maturity debt securities, fair value	442,366	451,353
State And Municipal Obligations | Quoted Prices in Active  Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities:	0	0
Held to maturity debt securities, fair value	0	0
State And Municipal Obligations | Significant Other Observable  Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities:	4,049	4,079
Held to maturity debt securities, fair value	442,366	451,353
State And Municipal Obligations | Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities:	0	0
Held to maturity debt securities, fair value	0	0
Corporate Obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities:	25,607	25,410
Held to maturity debt securities, fair value	9,318	9,890
Corporate Obligations | Quoted Prices in Active  Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities:	0	0
Held to maturity debt securities, fair value	0	0
Corporate Obligations | Significant Other Observable  Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities:	25,607	25,410
Held to maturity debt securities, fair value	9,318	9,890
Corporate Obligations | Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities:	0	0
Held to maturity debt securities, fair value	0	0
Measured on a Recurring Basis
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities:	989,833	976,919
Equity securities	685	825
Derivative assets	111,608	39,305
Total assets at fair value	1,102,126	1,017,049
Derivative liabilities	120,176	39,356
Measured on a Recurring Basis | Quoted Prices in Active  Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities:	0	0
Equity securities	685	825
Derivative assets	0	0
Total assets at fair value	685	825
Derivative liabilities	0	0
Measured on a Recurring Basis | Significant Other Observable  Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities:	989,833	976,919
Equity securities	0	0
Derivative assets	111,608	39,305
Total assets at fair value	1,101,441	1,016,224
Derivative liabilities	120,176	39,356
Measured on a Recurring Basis | Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities:	0	0
Equity securities	0	0
Derivative assets	0	0
Total assets at fair value	0	0
Derivative liabilities	0	0
Measured on a Recurring Basis | Mortgage-Backed Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities:	960,177	947,430
Measured on a Recurring Basis | Mortgage-Backed Securities | Quoted Prices in Active  Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities:	0	0
Measured on a Recurring Basis | Mortgage-Backed Securities | Significant Other Observable  Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities:	960,177	947,430
Measured on a Recurring Basis | Mortgage-Backed Securities | Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities:	0	0
Measured on a Recurring Basis | State And Municipal Obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities:	4,049	4,079
Measured on a Recurring Basis | State And Municipal Obligations | Quoted Prices in Active  Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities:	0	0
Measured on a Recurring Basis | State And Municipal Obligations | Significant Other Observable  Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities:	4,049	4,079
Measured on a Recurring Basis | State And Municipal Obligations | Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities:	0	0
Measured on a Recurring Basis | Corporate Obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities:	25,607	25,410
Measured on a Recurring Basis | Corporate Obligations | Quoted Prices in Active  Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities:	0	0
Measured on a Recurring Basis | Corporate Obligations | Significant Other Observable  Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities:	25,607	25,410
Measured on a Recurring Basis | Corporate Obligations | Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities:	0	0
Measured on a Non-Recurring Basis
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets at fair value	20,114	23,118
Loans measured for impairment based on the fair value of the underlying collateral	15,895	20,403
Foreclosed assets	4,219	2,715
Measured on a Non-Recurring Basis | Quoted Prices in Active  Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets at fair value	0	0
Loans measured for impairment based on the fair value of the underlying collateral	0	0
Foreclosed assets	0	0
Measured on a Non-Recurring Basis | Significant Other Observable  Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets at fair value	0	0
Loans measured for impairment based on the fair value of the underlying collateral	0	0
Foreclosed assets	0	0
Measured on a Non-Recurring Basis | Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets at fair value	20,114	23,118
Loans measured for impairment based on the fair value of the underlying collateral	15,895	20,403
Foreclosed assets	$ 4,219	$ 2,715