Allowance for Credit Losses - Schedule of Aging of the Company's Loan Portfolio (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024	Mar. 31, 2024
Financing Receivable, Past Due [Line Items]
Nonaccrual	$ 151,203	$ 154,641	$ 122,408
Loans, net of unearned income	48,708,390	48,055,037	43,230,706
Early buy-out loans guaranteed by U.S. government agencies
Financing Receivable, Past Due [Line Items]
Nonaccrual	0	0	0
Loans, net of unearned income	123,742	156,756	143,350
Commercial, industrial and other
Financing Receivable, Past Due [Line Items]
Nonaccrual	70,560	73,490	31,740
Loans, net of unearned income	15,931,326	15,574,551	13,503,481
Commercial real estate
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	12,914,901	12,903,944	11,633,437
Commercial real estate | Construction and development
Financing Receivable, Past Due [Line Items]
Nonaccrual	3,613	2,282	1,627
Loans, net of unearned income	2,448,881	2,434,081	2,150,314
Commercial real estate | Non-construction
Financing Receivable, Past Due [Line Items]
Nonaccrual	22,574	18,760	37,635
Loans, net of unearned income	10,466,020	10,469,863	9,483,123
Home equity
Financing Receivable, Past Due [Line Items]
Nonaccrual	2,070	1,117	838
Loans, net of unearned income	455,683	445,028	340,349
Residential real estate, excluding early buy-out loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	3,685,159	3,612,765	2,890,266
Residential real estate, excluding early buy-out loans | Residential real estate, excluding early buy-out loans
Financing Receivable, Past Due [Line Items]
Nonaccrual	22,522	23,762	17,901
Loans, net of unearned income	3,561,417	3,456,009	2,746,916
Premium finance receivables | Property and casualty insurance loans
Financing Receivable, Past Due [Line Items]
Nonaccrual	29,846	28,797	32,648
Loans, net of unearned income	7,239,862	7,272,042	6,940,019
Premium finance receivables | Life insurance loans
Financing Receivable, Past Due [Line Items]
Nonaccrual	0	6,431	0
Loans, net of unearned income	8,365,140	8,147,145	7,872,033
Consumer and other
Financing Receivable, Past Due [Line Items]
Nonaccrual	18	2	19
Loans, net of unearned income	116,319	99,562	51,121
Total loans, net of unearned income, excluding early buy-out loans
Financing Receivable, Past Due [Line Items]
Nonaccrual	151,203	154,641	122,408
Loans, net of unearned income	48,584,648	47,898,281	43,087,356
90+ days and still accruing
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	51,647	50,134	76,168
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	30,460	33,952	50,217
90+ days and still accruing | Commercial, industrial and other
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	46	104	27
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	0
90+ days and still accruing | Residential real estate, excluding early buy-out loans | 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	18,081	16,031	25,877
90+ days and still accruing | Premium finance receivables | Life insurance loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	2,962	0	0
90+ days and still accruing | Consumer and other
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	98	47	47
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	21,187	16,182	25,951
60-89 days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	56,496	164,988	94,945
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	1,457	618	0
60-89 days past due | Commercial, industrial and other
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	15,243	54,844	30,248
60-89 days past due | Commercial real estate | Construction and development
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	820	1,339	818
60-89 days past due | Commercial real estate | Non-construction
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	6,175	9,182	15,895
60-89 days past due | Home equity
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	984	1,233	212
60-89 days past due | Residential real estate, excluding early buy-out loans | Residential real estate, excluding early buy-out loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	1,351	5,708	0
60-89 days past due | Premium finance receivables | Property and casualty insurance loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	19,717	19,042	15,274
60-89 days past due | Premium finance receivables | Life insurance loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	10,587	72,963	32,482
60-89 days past due | Consumer and other
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	162	59	16
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	55,039	164,370	94,945
30-59 days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	295,446	252,223	297,976
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	2,125	2,335	1,047
30-59 days past due | Commercial, industrial and other
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	97,397	92,551	77,715
30-59 days past due | Commercial real estate | Construction and development
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	3,994	4,634	7,066
30-59 days past due | Commercial real estate | Non-construction
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	79,659	26,132	25,932
30-59 days past due | Home equity
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	3,403	2,148	1,617
30-59 days past due | Residential real estate, excluding early buy-out loans | Residential real estate, excluding early buy-out loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	38,943	18,917	24,523
30-59 days past due | Premium finance receivables | Property and casualty insurance loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	39,459	68,219	59,729
30-59 days past due | Premium finance receivables | Life insurance loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	29,924	36,405	100,137
30-59 days past due | Consumer and other
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	542	882	210
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	293,321	249,888	296,929
Current
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	48,153,598	47,433,051	42,639,209
Current | Early buy-out loans guaranteed by U.S. government agencies
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	89,700	119,851	92,086
Current | Commercial, industrial and other
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	15,748,080	15,353,562	13,363,751
Current | Commercial real estate | Construction and development
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	2,440,454	2,425,826	2,140,803
Current | Commercial real estate | Non-construction
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	10,357,612	10,415,789	9,403,661
Current | Home equity
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	449,226	440,530	337,682
Current | Residential real estate, excluding early buy-out loans | Residential real estate, excluding early buy-out loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	3,498,601	3,407,622	2,704,492
Current | Premium finance receivables | Property and casualty insurance loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	7,132,759	7,139,953	6,806,491
Current | Premium finance receivables | Life insurance loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	8,321,667	8,031,346	7,739,414
Current | Consumer and other
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	115,499	98,572	50,829
Current | Total loans, net of unearned income, excluding early buy-out loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	$ 48,063,898	$ 47,313,200	$ 42,547,123