Fair Value Disclosures - Schedule of Estimated Fair Values and Carrying Values of All Financial Instruments (Detail) - USD ($)	Jun. 30, 2022	Dec. 31, 2021	Jun. 30, 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	$ 242,665,000	$ 205,053,000	$ 190,061,000
Interest-bearing Deposits in Banks and Other Financial Institutions	222,899,000	323,535,000	654,531,000
Securities available-for-sale, Estimated Fair Value	6,215,036,000	6,573,179,000	5,578,048,000
Loans held-for-investment, net of allowance for credit losses	5,806,650,000	5,325,507,000	5,242,464,000
Loans held for sale	26,445,000	37,810,000	61,802,000
Borrowings	768,364,000	671,152,000	549,969,000
IRLCs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset Derivative Fair Value	1,414,000	1,279,000	2,670,000
Liability Derivative Fair Value	0	0	0
Forward Mortgage-Backed Securities Trades [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset Derivative Fair Value	58,000	0	0
Liability Derivative Fair Value	0	147,000	376,000
Carrying Value [Member] | Level 1 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	242,665,000	205,053,000	190,061,000
Interest-bearing Deposits in Banks and Other Financial Institutions	222,899,000	323,535,000	654,531,000
Deposits with no stated maturities	10,681,596,000	10,105,073,000	9,311,213,000
Carrying Value [Member] | Level 2 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held for sale	26,445,000	37,810,000	61,802,000
Accrued interest receivable	58,047,000	57,169,000	54,128,000
Deposits with stated maturities	441,387,000	461,415,000	470,481,000
Borrowings	768,364,000	671,152,000	549,969,000
Accrued interest payable	423,000	221,000	316,000
Carrying Value [Member] | Level 2 Inputs [Member] | IRLCs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset Derivative Fair Value	1,414,000	1,279,000	2,670,000
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	58,000	(147,000)	(376,000)
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	6,215,036,000	6,573,179,000	5,578,048,000
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	5,806,650,000	5,325,507,000	5,242,464,000
Estimated Fair Value [Member] | Level 1 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	242,665,000	205,053,000	190,061,000
Interest-bearing Deposits in Banks and Other Financial Institutions	222,899,000	323,535,000	654,531,000
Deposits with no stated maturities	10,681,596,000	10,105,073,000	9,311,213,000
Estimated Fair Value [Member] | Level 2 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held for sale	26,445,000	37,844,000	61,969,000
Accrued interest receivable	58,047,000	57,169,000	54,128,000
Deposits with stated maturities	439,546,000	462,312,000	471,857,000
Borrowings	768,364,000	671,152,000	549,969,000
Accrued interest payable	423,000	221,000	316,000
Estimated Fair Value [Member] | Level 2 Inputs [Member] | IRLCs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset Derivative Fair Value	1,414,000	1,279,000	2,670,000
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	58,000	(147,000)	(376,000)
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	6,215,036,000	6,573,179,000	5,578,048,000
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	$ 5,852,415,000	$ 5,335,791,000	$ 5,273,264,000