Allowance for Credit Losses - Schedule of Aging of the Company's Loan Portfolio (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023
Financing Receivable, Past Due [Line Items]
Nonaccrual	$ 161,059		$ 104,967
Loans, net of unearned income	47,067,447	$ 42,131,831	41,446,032
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	135,389	150,583	168,973
Commercial
Financing Receivable, Past Due [Line Items]
Nonaccrual	63,826	38,940	43,569
Loans, net of unearned income	15,247,693	12,832,053	12,725,473
Commercial real estate
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	12,793,417	11,344,164	10,946,180
Commercial real estate | Construction and development
Financing Receivable, Past Due [Line Items]
Nonaccrual	2,284	2,205	8,384
Loans, net of unearned income	2,403,690	2,084,041	1,893,773
Commercial real estate | Non-construction
Financing Receivable, Past Due [Line Items]
Nonaccrual	39,787	33,254	8,659
Loans, net of unearned income	10,389,727	9,260,123	9,052,407
Home equity
Financing Receivable, Past Due [Line Items]
Nonaccrual	1,122	1,341	1,363
Loans, net of unearned income	427,043	343,976	343,258
Residential real estate
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	3,388,038	2,769,666	2,707,603
Residential real estate | Residential real estate, excluding early buy-out loans
Financing Receivable, Past Due [Line Items]
Nonaccrual	17,959	15,391	16,103
Loans, net of unearned income	3,252,649	2,619,083	2,538,630
Premium finance receivables | Property and casualty insurance loans
Financing Receivable, Past Due [Line Items]
Nonaccrual	36,079	27,590	26,756
Loans, net of unearned income	7,131,681	6,903,529	6,722,747
Premium finance receivables | Life insurance loans
Financing Receivable, Past Due [Line Items]
Nonaccrual	0	0	0
Loans, net of unearned income	7,996,899	7,877,943	7,931,808
Consumer and other
Financing Receivable, Past Due [Line Items]
Nonaccrual	2	22	16
Loans, net of unearned income	82,676	60,500	68,963
Total loans, net of unearned income, excluding early buy-out loans
Financing Receivable, Past Due [Line Items]
Nonaccrual	161,059	118,743	104,850
Loans, net of unearned income	46,932,058	41,981,248	41,277,059
90+ days and still accruing
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	61,986	77,975	85,809
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	43,358	57,688	57,558
90+ days and still accruing | Commercial
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	20	98	200
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	225	0	1,092
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 | 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	18,235	20,135	16,253
90+ days and still accruing | Premium finance receivables | Life insurance loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	0	0	10,679
90+ days and still accruing | Consumer and other
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	148	54	27
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	18,628	20,287	28,251
60-89 days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	83,212	70,107	92,406
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	150	250	2,116
60-89 days past due | Commercial
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	32,560	19,488	22,889
60-89 days past due | Commercial real estate | Construction and development
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	757	251	2,438
60-89 days past due | Commercial real estate | Non-construction
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	12,682	8,264	4,957
60-89 days past due | Home equity
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	1,035	62	219
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	6,364	2,325	1,145
60-89 days past due | Premium finance receivables | Property and casualty insurance loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	18,740	23,236	16,552
60-89 days past due | Premium finance receivables | Life insurance loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	10,902	16,206	41,894
60-89 days past due | Consumer and other
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	22	25	196
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	83,062	69,857	90,290
30-59 days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	204,043	227,976	146,647
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	46,057	85,743	35,681
30-59 days past due | Commercial real estate | Construction and development
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	1,798	1,343	31,292
30-59 days past due | Commercial real estate | Non-construction
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	46,548	19,291	29,692
30-59 days past due | Home equity
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	2,580	2,263	1,668
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	2,160	22,942	904
30-59 days past due | Premium finance receivables | Property and casualty insurance loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	30,204	50,437	31,919
30-59 days past due | Premium finance receivables | Life insurance loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	74,432	45,464	14,972
30-59 days past due | Consumer and other
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	264	165	519
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	204,043	227,648	146,647
Current
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	46,557,147	41,637,030	41,016,203
Current | Early buy-out loans guaranteed by U.S. government agencies
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	91,881	92,317	109,182
Current | Commercial
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	15,105,230	12,687,784	12,623,134
Current | Commercial real estate | Construction and development
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	2,398,851	2,080,242	1,851,659
Current | Commercial real estate | Non-construction
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	10,290,485	9,199,314	9,008,007
Current | Home equity
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	422,306	340,310	340,008
Current | Residential real estate | Residential real estate, excluding early buy-out loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	3,226,166	2,578,425	2,520,478
Current | Premium finance receivables | Property and casualty insurance loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	7,028,423	6,782,131	6,631,267
Current | Premium finance receivables | Life insurance loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	7,911,565	7,816,273	7,864,263
Current | Consumer and other
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	82,240	60,234	68,205
Current | Total loans, net of unearned income, excluding early buy-out loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	$ 46,465,266	$ 41,544,713	$ 40,907,021