Loans (Summary of Loan Portfolio) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Loans [Line Items]
Total loans, net of unearned income	$ 34,789,104	$ 32,079,073
Total loans, net of unearned income, percentage	100.00%	100.00%
Commercial
Loans [Line Items]
Total loans, net of unearned income	$ 11,904,068	$ 11,955,967
Total loans, net of unearned income, percentage	34.00%	37.00%
Commercial real estate
Loans [Line Items]
Total loans, net of unearned income	$ 8,990,286	$ 8,494,132
Total loans, net of unearned income, percentage	26.00%	26.00%
Home equity
Loans [Line Items]
Total loans, net of unearned income	$ 335,155	$ 425,263
Total loans, net of unearned income, percentage	1.00%	1.00%
Residential real estate
Loans [Line Items]
Total loans, net of unearned income	$ 1,637,099	$ 1,259,598
Total loans, net of unearned income, percentage	5.00%	5.00%
Premium finance receivables | Property & casualty
Loans [Line Items]
Total loans, net of unearned income	$ 4,855,487	$ 4,054,489
Total loans, net of unearned income, percentage	14.00%	13.00%
Premium finance receivables | Life insurance
Loans [Line Items]
Total loans, net of unearned income	$ 7,042,810	$ 5,857,436
Total loans, net of unearned income, percentage	20.00%	18.00%
Consumer and other
Loans [Line Items]
Total loans, net of unearned income	$ 24,199	$ 32,188
Total loans, net of unearned income, percentage	0.00%	0.00%