Fair Value Disclosures - Schedule of Estimated Fair Values and Carrying Values of All Financial Instruments (Detail) - USD ($)	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	$ 203,187,000	$ 205,053,000	$ 190,350,000
Interest-bearing Deposits in Banks and Other Financial Institutions	394,566,000	323,535,000	893,221,000
Securities available-for-sale, Estimated Fair Value	6,502,495,000	6,573,179,000	5,109,631,000
Loans held-for-investment, net of allowance for credit losses	5,499,256,000	5,325,507,000	5,259,588,000
Loans held for sale	27,670,000	37,810,000	65,405,000
Borrowings	758,595,000	671,152,000	548,604,000
IRLCs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset Derivative Fair Value	276,000	1,279,000	1,645,000
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	2,103,000	0	2,806,000
Liability Derivative Fair Value	0	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	203,187,000	205,053,000	190,350,000
Interest-bearing Deposits in Banks and Other Financial Institutions	394,566,000	323,535,000	893,221,000
Deposits with no stated maturities	10,550,695,000	10,105,073,000	8,929,762,000
Carrying Value [Member] | Level 2 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held for sale	27,670,000	37,810,000	65,405,000
Accrued interest receivable	48,066,000	57,169,000	42,322,000
Deposits with stated maturities	449,130,000	461,415,000	483,685,000
Borrowings	758,595,000	671,152,000	548,604,000
Accrued interest payable	268,000	221,000	320,000
Carrying Value [Member] | Level 2 Inputs [Member] | IRLCs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset Derivative Fair Value	276,000	1,279,000	1,645,000
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	2,103,000	(147,000)	2,806,000
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	6,502,495,000	6,573,179,000	5,109,631,000
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	5,499,256,000	5,325,507,000	5,259,588,000
Estimated Fair Value [Member] | Level 1 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	203,187,000	205,053,000	190,350,000
Interest-bearing Deposits in Banks and Other Financial Institutions	394,566,000	323,535,000	893,221,000
Deposits with no stated maturities	10,550,695,000	10,105,073,000	8,929,762,000
Estimated Fair Value [Member] | Level 2 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held for sale	26,985,000	37,844,000	65,273,000
Accrued interest receivable	48,066,000	57,169,000	42,322,000
Deposits with stated maturities	449,987,000	462,312,000	485,193,000
Borrowings	758,595,000	671,152,000	548,604,000
Accrued interest payable	268,000	221,000	320,000
Estimated Fair Value [Member] | Level 2 Inputs [Member] | IRLCs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset Derivative Fair Value	276,000	1,279,000	1,645,000
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	2,103,000	(147,000)	(2,806,000)
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	6,502,495,000	6,573,179,000	5,109,631,000
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	$ 5,522,778,000	$ 5,335,791,000	$ 5,273,235,000