Loans - Schedule of Loan Portfolio (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024	Mar. 31, 2024
Loans [Line Items]
Total loans, net of unearned income	$ 48,708,390	$ 48,055,037	$ 43,230,706
Total loans, net of unearned income, percentage	100.00%	100.00%	100.00%
Commercial
Loans [Line Items]
Total loans, net of unearned income	$ 15,931,326	$ 15,574,551	$ 13,503,481
Total loans, net of unearned income, percentage	33.00%	32.00%	31.00%
Commercial real estate
Loans [Line Items]
Total loans, net of unearned income	$ 12,914,901	$ 12,903,944	$ 11,633,437
Total loans, net of unearned income, percentage	26.00%	27.00%	27.00%
Home equity
Loans [Line Items]
Total loans, net of unearned income	$ 455,683	$ 445,028	$ 340,349
Total loans, net of unearned income, percentage	1.00%	1.00%	1.00%
Residential real estate
Loans [Line Items]
Total loans, net of unearned income	$ 3,685,159	$ 3,612,765	$ 2,890,266
Total loans, net of unearned income, percentage	8.00%	8.00%	7.00%
Premium finance receivables | Premium finance receivables—property & casualty
Loans [Line Items]
Total loans, net of unearned income	$ 7,239,862	$ 7,272,042	$ 6,940,019
Total loans, net of unearned income, percentage	15.00%	15.00%	16.00%
Premium finance receivables | Premium finance receivables—life insurance
Loans [Line Items]
Total loans, net of unearned income	$ 8,365,140	$ 8,147,145	$ 7,872,033
Total loans, net of unearned income, percentage	17.00%	17.00%	18.00%
Consumer and other
Loans [Line Items]
Total loans, net of unearned income	$ 116,319	$ 99,562	$ 51,121
Total loans, net of unearned income, percentage	0.00%	0.00%	0.00%