Fair Value Disclosures - Schedule of Estimated Fair Values and Carrying Values of All Financial Instruments (Detail) - USD ($)	Sep. 30, 2022	Dec. 31, 2021	Sep. 30, 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	$ 227,298,000	$ 205,053,000	$ 201,901,000
Interest-Bearing Deposits in Banks and Other Financial Institutions	138,484,000	323,535,000	359,241,000
Securities available-for-sale, Estimated Fair Value	5,745,443,000	6,573,179,000	6,119,984,000
Loans held-for-investment, net of allowance for credit losses	6,181,380,000	5,325,507,000	5,223,124,000
Loans held for sale	18,815,000	37,810,000	47,721,000
Borrowings	774,581,000	671,152,000	648,679,000
IRLCs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset Derivative Fair Value		1,279,000	1,701,000
Liability Derivative Fair Value	251,000	0	0
Forward Mortgage-Backed Securities Trades [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset Derivative Fair Value	1,897,000	0	828,000
Liability Derivative Fair Value		147,000	0
Carrying Value [Member] | Level 1 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	227,298,000	205,053,000	201,901,000
Interest-Bearing Deposits in Banks and Other Financial Institutions	138,484,000	323,535,000	359,241,000
Deposits with no stated maturities	10,724,016,000	10,105,073,000	9,423,250,000
Carrying Value [Member] | Level 2 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held for sale	18,815,000	37,810,000	47,721,000
Accrued interest receivable	49,416,000	57,169,000	43,516,000
Deposits with stated maturities	418,102,000	461,415,000	469,867,000
Borrowings	774,581,000	671,152,000	648,679,000
Accrued interest payable	494,000	221,000	294,000
Carrying Value [Member] | Level 2 Inputs [Member] | IRLCs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset Derivative Fair Value	(251,000)	1,279,000	1,701,000
Carrying Value [Member] | Level 2 Inputs [Member] | Forward Mortgage-Backed Securities Trades [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liability Derivative Fair Value	1,897,000	(147,000)	(828,000)
Carrying Value [Member] | Levels 1 and 2 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available-for-sale, Estimated Fair Value	5,745,443,000	6,573,179,000	6,119,984,000
Carrying Value [Member] | Level 3 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held-for-investment, net of allowance for credit losses	6,181,380,000	5,325,507,000	5,223,124,000
Estimated Fair Value [Member] | Level 1 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	227,298,000	205,053,000	201,901,000
Interest-Bearing Deposits in Banks and Other Financial Institutions	138,484,000	323,535,000	359,241,000
Deposits with no stated maturities	10,724,016,000	10,105,073,000	9,423,250,000
Estimated Fair Value [Member] | Level 2 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held for sale	18,815,000	37,844,000	47,748,000
Accrued interest receivable	49,416,000	57,169,000	43,516,000
Deposits with stated maturities	416,400,000	462,312,000	470,985,000
Borrowings	774,581,000	671,152,000	648,679,000
Accrued interest payable	494,000	221,000	294,000
Estimated Fair Value [Member] | Level 2 Inputs [Member] | IRLCs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset Derivative Fair Value	(251,000)	1,279,000	1,701,000
Estimated Fair Value [Member] | Level 2 Inputs [Member] | Forward Mortgage-Backed Securities Trades [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liability Derivative Fair Value	1,897,000	(147,000)	(828,000)
Estimated Fair Value [Member] | Levels 1 and 2 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available-for-sale, Estimated Fair Value	5,745,443,000	6,573,179,000	6,119,984,000
Estimated Fair Value [Member] | Level 3 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held-for-investment, net of allowance for credit losses	$ 6,215,441,000	$ 5,335,791,000	$ 5,236,471,000