Fair Value Measurements - Assets and Liabilities at Fair Values (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	$ 976,919	$ 1,063,079
Equity securities, at fair value	825	635
Foreclosed assets	2,715	1,565
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities, at fair value	825
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities, at fair value	0
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities, at fair value	0
Measured on a recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	976,919	1,063,079
Equity securities, at fair value	825	635
Derivative assets	39,305	15,634
Assets, fair value disclosure	1,017,049	1,079,348
Derivative liabilities	39,356	14,766
Measured on a recurring basis | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	0	0
Equity securities, at fair value	825	635
Derivative assets	0	0
Assets, fair value disclosure	825	635
Derivative liabilities	0	0
Measured on a recurring basis | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	976,919	1,063,079
Equity securities, at fair value	0	0
Derivative assets	39,305	15,634
Assets, fair value disclosure	1,016,224	1,078,713
Derivative liabilities	39,356	14,766
Measured on a recurring basis | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	0	0
Equity securities, at fair value	0	0
Derivative assets		0
Assets, fair value disclosure	0	0
Derivative liabilities	0	0
Measured on a non-recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure	23,118	4,285
Loans measured for impairment based on the fair value of the underlying collateral	20,403	4,285
Foreclosed assets	2,715	1,565
Measured on a non-recurring basis | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure	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 | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure	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 | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure	23,118	4,285
Loans measured for impairment based on the fair value of the underlying collateral	20,403	4,285
Foreclosed assets	2,715	1,565
Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	947,430	1,034,969
Mortgage-backed securities | Measured on a recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	947,430	1,034,969
Mortgage-backed securities | Measured on a recurring basis | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	0	0
Mortgage-backed securities | Measured on a recurring basis | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	947,430	1,034,969
Mortgage-backed securities | Measured on a recurring basis | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	0	0
State and municipal obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	4,079	2,912
State and municipal obligations | Measured on a recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	4,079	2,912
State and municipal obligations | Measured on a recurring basis | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	0	0
State and municipal obligations | Measured on a recurring basis | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	4,079	2,912
State and municipal obligations | Measured on a recurring basis | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	0	0
Corporate obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	25,410	25,198
Corporate obligations | Measured on a recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	25,410	25,198
Corporate obligations | Measured on a recurring basis | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	0	0
Corporate obligations | Measured on a recurring basis | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	25,410	25,198
Corporate obligations | Measured on a recurring basis | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	$ 0	$ 0