Fair Value of Financial Instruments - Fair Value Estimates (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Assets
HTM investment securities	$ 1,447,697	$ 1,485,506
AFS investment securities	1,154,021	1,140,071
Derivative Assets	46,368	44,939
Accrued interest receivable	67,642	68,516
Liabilities
Derivative Liabilities	12,369	13,603
Level 1
Assets
Cash and cash equivalents	1,028,818	936,473
HTM investment securities	0	0
AFS investment securities	0	0
Equity securities	631	759
Loans held for investment, net	0	0
Derivative Assets	8	1
Accrued interest receivable	0	0
Liabilities
Deposit accounts	0	0
FHLB advances	0	0
Subordinated debentures	0	0
Derivative Liabilities	0	10
Accrued interest payable	0	0
Level 1 | Interest-bearing time deposits with financial institutions
Assets
Cash and cash equivalents	995	995
Level 2
Assets
Cash and cash equivalents	0	0
HTM investment securities	1,447,697	1,485,506
AFS investment securities	1,154,021	1,140,071
Equity securities	0	0
Loans held for investment, net	0	0
Derivative Assets	6,488	5,643
Accrued interest receivable	67,642	68,516
Liabilities
Deposit accounts	15,200,489	15,003,769
FHLB advances	199,084	592,480
Subordinated debentures	321,657	320,687
Derivative Liabilities	12,019	10,705
Accrued interest payable	13,903	18,671
Level 2 | Interest-bearing time deposits with financial institutions
Assets
Cash and cash equivalents	0	0
Level 3
Assets
Cash and cash equivalents	0	0
HTM investment securities	0	0
AFS investment securities	0	0
Equity securities	0	0
Loans held for investment, net	12,304,608	12,562,323
Derivative Assets	0	0
Accrued interest receivable	0	0
Liabilities
Deposit accounts	0	0
FHLB advances	0	0
Subordinated debentures	0	0
Derivative Liabilities	0	0
Accrued interest payable	0	0
Level 3 | Interest-bearing time deposits with financial institutions
Assets
Cash and cash equivalents	0	0
Carrying Amount
Assets
Cash and cash equivalents	1,028,818	936,473
HTM investment securities	1,720,481	1,729,541
AFS investment securities	1,154,021	1,140,071
Equity securities	631	759
Loans held for investment, net	13,012,071	13,289,020
Derivative Assets	6,496	5,644
Accrued interest receivable	67,642	68,516
Liabilities
Deposit accounts	15,187,828	14,995,626
FHLB advances	200,000	600,000
Subordinated debentures	332,001	331,842
Derivative Liabilities	12,019	10,715
Accrued interest payable	13,903	18,671
Carrying Amount | Interest-bearing time deposits with financial institutions
Assets
Cash and cash equivalents	995	995
Estimated Fair Value
Assets
Cash and cash equivalents	1,028,818	936,473
HTM investment securities	1,447,697	1,485,506
AFS investment securities	1,154,021	1,140,071
Equity securities	631	759
Loans held for investment, net	12,304,608	12,562,323
Derivative Assets	6,496	5,644
Accrued interest receivable	67,642	68,516
Liabilities
Deposit accounts	15,200,489	15,003,769
FHLB advances	199,084	592,480
Subordinated debentures	321,657	320,687
Derivative Liabilities	12,019	10,715
Accrued interest payable	13,903	18,671
Estimated Fair Value | Interest-bearing time deposits with financial institutions
Assets
Cash and cash equivalents	$ 995	$ 995