Allowance for Credit Losses - Schedule of Aging of the Company's Loan Portfolio (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023
Financing Receivable, Past Due [Line Items]
Nonaccrual	$ 151,399	$ 118,743	$ 93,666
Loans, net of unearned income	44,675,531	42,131,831	41,023,408
Early buy-out loans guaranteed by U.S. government agencies
Financing Receivable, Past Due [Line Items]
Nonaccrual	0	0	117
Loans, net of unearned income	134,178	150,583	187,848
Commercial
Financing Receivable, Past Due [Line Items]
Nonaccrual	51,087	38,940	40,460
Loans, net of unearned income	14,154,462	12,832,053	12,600,471
Commercial real estate
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	11,947,197	11,344,164	10,608,811
Commercial real estate | Construction and development
Financing Receivable, Past Due [Line Items]
Nonaccrual	2,528	2,205	12,536
Loans, net of unearned income	2,260,551	2,084,041	1,760,436
Commercial real estate | Non-construction
Financing Receivable, Past Due [Line Items]
Nonaccrual	45,761	33,254	5,947
Loans, net of unearned income	9,686,646	9,260,123	8,848,375
Home equity
Financing Receivable, Past Due [Line Items]
Nonaccrual	1,100	1,341	1,361
Loans, net of unearned income	356,313	343,976	336,974
Residential real estate
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	3,067,335	2,769,666	2,643,240
Residential real estate | Residential real estate, excluding early buy-out loans
Financing Receivable, Past Due [Line Items]
Nonaccrual	18,198	15,391	13,652
Loans, net of unearned income	2,933,157	2,619,083	2,455,392
Premium finance receivables | Property and casualty insurance loans
Financing Receivable, Past Due [Line Items]
Nonaccrual	32,722	27,590	19,583
Loans, net of unearned income	7,100,753	6,903,529	6,762,698
Premium finance receivables | Life insurance loans
Financing Receivable, Past Due [Line Items]
Nonaccrual	0	0	6
Loans, net of unearned income	7,962,115	7,877,943	8,039,273
Consumer and other
Financing Receivable, Past Due [Line Items]
Nonaccrual	3	22	4
Loans, net of unearned income	87,356	60,500	31,941
Total loans, net of unearned income, excluding early buy-out loans
Financing Receivable, Past Due [Line Items]
Nonaccrual	151,399	118,743	93,549
Loans, net of unearned income	44,541,353	41,981,248	40,835,560
90+ days and still accruing
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	68,640	77,975	72,891
90+ days and still accruing | Early buy-out loans guaranteed by U.S. government agencies
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	45,788	57,688	57,728
90+ days and still accruing | Commercial
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	304	98	573
90+ days and still accruing | Commercial real estate | Construction and development
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	0	0	0
90+ days and still accruing | Commercial real estate | Non-construction
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	0	0	0
90+ days and still accruing | Home equity
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	0	0	110
90+ days and still accruing | Residential real estate | Residential real estate, excluding early buy-out loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	0	0	0
90+ days and still accruing | Premium finance receivables | Property and casualty insurance loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	22,427	20,135	12,785
90+ days and still accruing | Premium finance receivables | Life insurance loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	0	0	1,667
90+ days and still accruing | Consumer and other
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	121	54	28
90+ days and still accruing | Total loans, net of unearned income, excluding early buy-out loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	22,852	20,287	15,163
60-89 days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	59,416	70,107	58,789
60-89 days past due | Early buy-out loans guaranteed by U.S. government agencies
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	0	250	918
60-89 days past due | Commercial
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	16,485	19,488	22,808
60-89 days past due | Commercial real estate | Construction and development
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	1,699	251	0
60-89 days past due | Commercial real estate | Non-construction
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	4,856	8,264	1,054
60-89 days past due | Home equity
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	275	62	316
60-89 days past due | Residential real estate | Residential real estate, excluding early buy-out loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	1,977	2,325	7,243
60-89 days past due | Premium finance receivables | Property and casualty insurance loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	29,925	23,236	22,670
60-89 days past due | Premium finance receivables | Life insurance loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	4,118	16,206	3,729
60-89 days past due | Consumer and other
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	81	25	51
60-89 days past due | Total loans, net of unearned income, excluding early buy-out loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	59,416	69,857	57,871
30-59 days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	139,768	227,976	187,675
30-59 days past due | Early buy-out loans guaranteed by U.S. government agencies
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	0	328	0
30-59 days past due | Commercial
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	36,358	85,743	48,970
30-59 days past due | Commercial real estate | Construction and development
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	6,539	1,343	766
30-59 days past due | Commercial real estate | Non-construction
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	31,526	19,291	13,452
30-59 days past due | Home equity
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	1,229	2,263	601
30-59 days past due | Residential real estate | Residential real estate, excluding early buy-out loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	130	22,942	872
30-59 days past due | Premium finance receivables | Property and casualty insurance loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	45,927	50,437	32,751
30-59 days past due | Premium finance receivables | Life insurance loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	17,693	45,464	90,117
30-59 days past due | Consumer and other
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	366	165	146
30-59 days past due | Total loans, net of unearned income, excluding early buy-out loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	139,768	227,648	187,675
Current
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	44,256,308	41,637,030	40,610,387
Current | Early buy-out loans guaranteed by U.S. government agencies
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	88,390	92,317	129,085
Current | Commercial
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	14,050,228	12,687,784	12,487,660
Current | Commercial real estate | Construction and development
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	2,249,785	2,080,242	1,747,134
Current | Commercial real estate | Non-construction
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	9,604,503	9,199,314	8,827,922
Current | Home equity
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	353,709	340,310	334,586
Current | Residential real estate | Residential real estate, excluding early buy-out loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	2,912,852	2,578,425	2,433,625
Current | Premium finance receivables | Property and casualty insurance loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	6,969,752	6,782,131	6,674,909
Current | Premium finance receivables | Life insurance loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	7,940,304	7,816,273	7,943,754
Current | Consumer and other
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	86,785	60,234	31,712
Current | Total loans, net of unearned income, excluding early buy-out loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	$ 44,167,918	$ 41,544,713	$ 40,481,302