Fair Value of Financial Instruments - Carrying Amount and Estimated Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Assets:
HTM investment securities	$ 1,097,096	$ 384,423
AFS investment securities	2,601,013	4,273,864
Total derivative assets	78,129	11,989
Accrued interest receivable	73,784	65,728
Liabilities:
FHLB advances	1,000,000	550,000
Derivative liabilities	12,598	5,263
Recurring
Assets:
AFS investment securities	2,601,013	4,273,864
Equity securities	13,526
Total derivative assets	8,948	11,989
Liabilities:
Derivative liabilities	12,531
Equity securities that are measured at NAV	12,600
Level 1
Assets:
Cash and cash equivalents	1,101,249	304,703
HTM investment securities	0	0
AFS investment securities	0	0
Equity securities	925
Loans held for sale	0	0
Loans held for investment, net	0	0
Total derivative assets	1	0
Accrued interest receivable	0	65,728
Liabilities:
Deposit accounts	0	16,057,316
FHLB advances	0	0
Other borrowings		0
Subordinated debentures	0	0
Derivative liabilities	1	0
Accrued interest payable	0	2,366
Level 1 | Recurring
Assets:
AFS investment securities	0	0
Equity securities	925
Total derivative assets	1	0
Liabilities:
Derivative liabilities	1
Level 1 | Interest-bearing time deposits with financial institutions
Assets:
Cash and cash equivalents	1,734	2,216
Level 2
Assets:
Cash and cash equivalents	0	0
HTM investment securities	1,097,096	384,423
AFS investment securities	2,601,013	4,273,864
Equity securities	0
Loans held for sale	2,755	11,959
Loans held for investment, net	0	0
Total derivative assets	7,053	10,100
Accrued interest receivable	73,784	0
Liabilities:
Deposit accounts	17,334,219	1,058,822
FHLB advances	982,695	550,093
Other borrowings		8,000
Subordinated debentures	327,609	350,359
Derivative liabilities	12,530	5,263
Accrued interest payable	14,661	0
Level 2 | Recurring
Assets:
AFS investment securities	2,601,013	4,273,864
Equity securities	0
Total derivative assets	7,053	10,100
Liabilities:
Derivative liabilities	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
Loans held for sale	0	0
Loans held for investment, net	13,846,403	14,392,684
Total derivative assets	1,894	1,889
Accrued interest receivable	0	0
Liabilities:
Deposit accounts	0	0
FHLB advances	0	0
Other borrowings		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
Total derivative assets	1,894	1,889
Liabilities:
Derivative liabilities	0
Level 3 | Interest-bearing time deposits with financial institutions
Assets:
Cash and cash equivalents	0	0
Carrying Amount
Assets:
Cash and cash equivalents	1,101,249	304,703
HTM investment securities	1,388,103	381,674
AFS investment securities	2,601,013	4,273,864
Equity securities	13,526
Loans held for sale	2,643	10,869
Loans held for investment, net	14,676,298	14,295,897
Total derivative assets	8,948	11,989
Accrued interest receivable	73,784	65,728
Liabilities:
Deposit accounts	17,352,401	17,115,589
FHLB advances	1,000,000	550,000
Other borrowings		8,000
Subordinated debentures	331,204	330,567
Derivative liabilities	12,531	5,263
Accrued interest payable	14,661	2,366
Carrying Amount | Interest-bearing time deposits with financial institutions
Assets:
Cash and cash equivalents	1,734	2,216
Estimated Fair Value
Assets:
Cash and cash equivalents	1,101,249	304,703
HTM investment securities	1,097,096	384,423
AFS investment securities	2,601,013	4,273,864
Equity securities	13,526
Loans held for sale	2,755	11,959
Loans held for investment, net	13,846,403	14,392,684
Total derivative assets	8,948	11,989
Accrued interest receivable	73,784	65,728
Liabilities:
Deposit accounts	17,334,219	17,116,138
FHLB advances	982,695	550,093
Other borrowings		8,000
Subordinated debentures	327,609	350,359
Derivative liabilities	12,531	5,263
Accrued interest payable	14,661	2,366
Estimated Fair Value | Interest-bearing time deposits with financial institutions
Assets:
Cash and cash equivalents	$ 1,734	$ 2,216