Loans - Schedule of Loan Portfolio (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025	Mar. 31, 2025
Loans [Line Items]
Total loans, net of unearned income	$ 54,071,292	$ 53,105,101	$ 48,708,390
Total loans, net of unearned income, percentage	100.00%	100.00%	100.00%
Commercial
Loans [Line Items]
Total loans, net of unearned income	$ 17,763,221	$ 17,044,686	$ 15,931,326
Total loans, net of unearned income, percentage	33.00%	32.00%	33.00%
Commercial real estate
Loans [Line Items]
Total loans, net of unearned income	$ 14,162,286	$ 13,940,736	$ 12,914,901
Total loans, net of unearned income, percentage	26.00%	26.00%	26.00%
Home equity
Loans [Line Items]
Total loans, net of unearned income	$ 471,264	$ 480,525	$ 455,683
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	$ 4,465,166	$ 4,317,232	$ 3,685,159
Total loans, net of unearned income, percentage	8.00%	8.00%	8.00%
Premium finance receivables—property & casualty \| Premium finance receivables—property & casualty
Loans [Line Items]
Total loans, net of unearned income	$ 7,890,331	$ 8,183,416	$ 7,239,862
Total loans, net of unearned income, percentage	15.00%	16.00%	15.00%
Premium finance receivables—property & casualty \| Premium finance receivables—life insurance
Loans [Line Items]
Total loans, net of unearned income	$ 9,196,382	$ 9,023,642	$ 8,365,140
Total loans, net of unearned income, percentage	17.00%	17.00%	17.00%
Consumer and other
Loans [Line Items]
Total loans, net of unearned income	$ 122,642	$ 114,864	$ 116,319
Total loans, net of unearned income, percentage	0.00%	0.00%	0.00%