Loans - Schedule of Loan Portfolio (Details) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024	Jun. 30, 2024
Loans [Line Items]
Total loans, net of unearned income	$ 51,041,679	$ 48,055,037	$ 44,675,531
Total loans, net of unearned income, percentage	100.00%	100.00%	100.00%
Commercial
Loans [Line Items]
Total loans, net of unearned income	$ 16,387,431	$ 15,574,551	$ 14,154,462
Total loans, net of unearned income, percentage	32.00%	32.00%	31.00%
Commercial real estate
Loans [Line Items]
Total loans, net of unearned income	$ 13,292,010	$ 12,903,944	$ 11,947,197
Total loans, net of unearned income, percentage	26.00%	27.00%	27.00%
Home equity
Loans [Line Items]
Total loans, net of unearned income	$ 466,815	$ 445,028	$ 356,313
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	$ 3,948,782	$ 3,612,765	$ 3,067,335
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	$ 8,323,176	$ 7,272,042	$ 7,100,753
Total loans, net of unearned income, percentage	16.00%	15.00%	16.00%
Premium finance receivables \| Premium finance receivables—life insurance
Loans [Line Items]
Total loans, net of unearned income	$ 8,506,960	$ 8,147,145	$ 7,962,115
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	$ 116,505	$ 99,562	$ 87,356
Total loans, net of unearned income, percentage	0.00%	0.00%	0.00%