Loans - Schedule of Loan Portfolio (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023
Loans [Line Items]
Total loans, net of unearned income	$ 44,675,531	$ 42,131,831	$ 41,023,408
Total loans, net of unearned income, percentage	100.00%	100.00%	100.00%
Commercial
Loans [Line Items]
Total loans, net of unearned income	$ 14,154,462	$ 12,832,053	$ 12,600,471
Total loans, net of unearned income, percentage	31.00%	30.00%	31.00%
Commercial real estate
Loans [Line Items]
Total loans, net of unearned income	$ 11,947,197	$ 11,344,164	$ 10,608,811
Total loans, net of unearned income, percentage	27.00%	27.00%	26.00%
Home equity
Loans [Line Items]
Total loans, net of unearned income	$ 356,313	$ 343,976	$ 336,974
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	$ 3,067,335	$ 2,769,666	$ 2,643,240
Total loans, net of unearned income, percentage	7.00%	7.00%	6.00%
Premium finance receivables | Premium finance receivables—property & casualty
Loans [Line Items]
Total loans, net of unearned income	$ 7,100,753	$ 6,903,529	$ 6,762,698
Total loans, net of unearned income, percentage	16.00%	16.00%	16.00%
Premium finance receivables | Premium finance receivables—life insurance
Loans [Line Items]
Total loans, net of unearned income	$ 7,962,115	$ 7,877,943	$ 8,039,273
Total loans, net of unearned income, percentage	18.00%	19.00%	20.00%
Consumer and other
Loans [Line Items]
Total loans, net of unearned income	$ 87,356	$ 60,500	$ 31,941
Total loans, net of unearned income, percentage	0.00%	0.00%	0.00%