Fair Value of Financial Instruments - Fair Value Estimates (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Assets
HTM investment securities	$ 1,496,494	$ 1,097,096
AFS investment securities	2,112,852	2,601,013
Derivative Assets	62,711	78,129
Accrued interest receivable	69,660	73,784
Liabilities
Derivative Liabilities	10,100	12,598
Recurring
Assets
AFS investment securities	2,112,852	2,601,013
Equity securities	962	13,526
Derivative Assets	6,079	8,948
Liabilities
Derivative Liabilities	10,577	12,531
Equity securities that are measured at NAV		12,600
Level 1
Assets
Cash and cash equivalents	1,424,896	1,101,249
HTM investment securities	0	0
AFS investment securities	0	0
Equity securities	962	925
Loans held for sale	0	0
Loans held for investment, net	0	0
Derivative Assets	37	1
Accrued interest receivable	0	0
Liabilities
Deposit accounts	0	0
FHLB advances	0	0
Subordinated debentures	0	0
Derivative Liabilities	8	1
Accrued interest payable	0	0
Level 1 | Recurring
Assets
AFS investment securities	0	0
Equity securities	962	925
Derivative Assets	37	1
Liabilities
Derivative Liabilities	8	1
Level 1 | Interest-bearing time deposits with financial institutions
Assets
Cash and cash equivalents	1,734	1,734
Level 2
Assets
Cash and cash equivalents	0	0
HTM investment securities	1,496,494	1,097,096
AFS investment securities	2,112,852	2,601,013
Equity securities	0	0
Loans held for sale	1,296	2,755
Loans held for investment, net	0	0
Derivative Assets	5,630	7,053
Accrued interest receivable	69,660	73,784
Liabilities
Deposit accounts	17,204,363	17,334,219
FHLB advances	788,132	982,695
Subordinated debentures	325,170	327,609
Derivative Liabilities	10,569	12,530
Accrued interest payable	23,261	14,661
Level 2 | Recurring
Assets
AFS investment securities	2,112,852	2,601,013
Equity securities	0	0
Derivative Assets	5,630	7,053
Liabilities
Derivative Liabilities	10,569	12,530
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 sale	0	0
Loans held for investment, net	13,412,607	13,846,403
Derivative Assets	412	1,894
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 | Recurring
Assets
AFS investment securities	0	0
Equity securities	0	0
Derivative Assets	412	1,894
Liabilities
Derivative Liabilities	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	1,424,896	1,101,249
HTM investment securities	1,749,030	1,388,103
AFS investment securities	2,112,852	2,601,013
Equity securities	962	13,526
Loans held for sale	1,247	2,643
Loans held for investment, net	14,171,784	14,676,298
Derivative Assets	6,079	8,948
Accrued interest receivable	69,660	73,784
Liabilities
Deposit accounts	17,207,810	17,352,401
FHLB advances	800,000	1,000,000
Subordinated debentures	331,364	331,204
Derivative Liabilities	10,577	12,531
Accrued interest payable	23,261	14,661
Carrying Amount | Interest-bearing time deposits with financial institutions
Assets
Cash and cash equivalents	1,734	1,734
Estimated Fair Value
Assets
Cash and cash equivalents	1,424,896	1,101,249
HTM investment securities	1,496,494	1,097,096
AFS investment securities	2,112,852	2,601,013
Equity securities	962	13,526
Loans held for sale	1,296	2,755
Loans held for investment, net	13,412,607	13,846,403
Derivative Assets	6,079	8,948
Accrued interest receivable	69,660	73,784
Liabilities
Deposit accounts	17,204,363	17,334,219
FHLB advances	788,132	982,695
Subordinated debentures	325,170	327,609
Derivative Liabilities	10,577	12,531
Accrued interest payable	23,261	14,661
Estimated Fair Value | Interest-bearing time deposits with financial institutions
Assets
Cash and cash equivalents	$ 1,734	$ 1,734