Fair Value Disclosures - Schedule of Estimated Fair Values and Carrying Values of All Financial Instruments (Detail) - USD ($)	6 Months Ended		12 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	$ 263,262,000	$ 255,018,000	$ 281,354,000
FEDERAL FUNDS SOLD	2,800,000	0	0
INTEREST-BEARING DEMAND DEPOSITS IN BANKS	103,315,000	23,839,000	255,237,000
Estimated Fair Value	4,573,024,000	5,066,262,000	4,732,762,000
Loans held-for-investment, net of allowance for credit losses	7,424,563,000	6,691,029,000	7,060,057,000
Loans held for sale	19,668,000	19,220,000	14,253,000
Borrowings	23,703,000	28,177,000	22,153,000
IRLCs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
IRLCs	518,000	455,000	427,000
Forward mortgage-backed securities trades asset (liability)	0	0	0
Forward Mortgage-Backed Securities Trades [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
IRLCs	0	160,000	0
Forward mortgage-backed securities trades asset (liability)	4,000	0	288,000
Carrying Value [Member] | Level 1 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	263,262,000	255,018,000	281,354,000
FEDERAL FUNDS SOLD	2,800,000	0	0
INTEREST-BEARING DEMAND DEPOSITS IN BANKS	103,315,000	23,839,000	255,237,000
Deposits with no stated maturities	10,439,355,000	9,914,131,000	10,199,320,000
Carrying Value [Member] | Level 2 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held for sale	19,668,000	19,220,000	14,253,000
Accrued interest receivable	61,847,000	56,236,000	58,544,000
Deposits with stated maturities	969,802,000	893,429,000	938,980,000
Repurchase Agreements	138,950,000	559,479,000	381,928,000
Borrowings	23,703,000	28,177,000	22,153,000
Accrued interest payable	10,092,000	8,155,000	10,215,000
Carrying Value [Member] | Level 2 Inputs [Member] | Forward Mortgage-Backed Securities Trades [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Forward mortgage-backed securities trades asset (liability)	(4,000)	160,000	(288,000)
Carrying Value [Member] | Levels 1 and 2 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value	4,573,024,000	5,066,262,000	4,732,762,000
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	7,424,563,000	6,691,029,000	7,060,057,000
Carrying Value [Member] | Level 3 Inputs [Member] | IRLCs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
IRLCs	518,000	455,000	427,000
Estimated Fair Value [Member] | Level 1 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	263,262,000	255,018,000	281,354,000
FEDERAL FUNDS SOLD	2,800,000	0	0
INTEREST-BEARING DEMAND DEPOSITS IN BANKS	103,315,000	23,839,000	255,237,000
Deposits with no stated maturities	10,439,355,000	9,914,131,000	10,199,320,000
Estimated Fair Value [Member] | Level 2 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held for sale	19,686,000	19,264,000	14,378,000
Accrued interest receivable	61,847,000	56,236,000	58,544,000
Deposits with stated maturities	969,750,000	891,181,000	938,534,000
Repurchase Agreements	138,950,000	559,479,000	381,928,000
Borrowings	23,703,000	28,177,000	22,153,000
Accrued interest payable	10,092,000	8,155,000	10,215,000
Estimated Fair Value [Member] | Level 2 Inputs [Member] | Forward Mortgage-Backed Securities Trades [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Forward mortgage-backed securities trades asset (liability)	(4,000)	160,000	(288,000)
Estimated Fair Value [Member] | Levels 1 and 2 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value	4,573,024,000	5,066,262,000	4,732,762,000
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	7,438,802,000	6,672,348,000	7,036,722,000
Estimated Fair Value [Member] | Level 3 Inputs [Member] | IRLCs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
IRLCs	$ 518,000	$ 455,000	$ 427,000