Loans (Summary of Loan Portfolio) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Loans [Line Items]
Loans, net of unearned income, excluding covered loans	$ 19,703,172	$ 17,118,117
Covered loans	58,145	148,673
Total loans	$ 19,761,317	$ 17,266,790
Total loans, percentage	100.00%	99.00%
Covered loans, percentage	0.00%	1.00%
Percentage of Loans Net of Unearned Income Including Covered Loans	100.00%	100.00%
Commercial
Loans [Line Items]
Loans, net of unearned income, excluding covered loans	$ 6,005,422	$ 4,713,909
Total loans, percentage	30.00%	27.00%
Commercial real estate
Loans [Line Items]
Loans, net of unearned income, excluding covered loans	$ 6,196,087	$ 5,529,289
Total loans, percentage	31.00%	32.00%
Home equity
Loans [Line Items]
Loans, net of unearned income, excluding covered loans	$ 725,793	$ 784,675
Total loans, percentage	4.00%	5.00%
Residential real estate
Loans [Line Items]
Loans, net of unearned income, excluding covered loans	$ 705,221	$ 607,451
Total loans, percentage	4.00%	3.00%
Premium finance receivables | Commercial insurance loans
Loans [Line Items]
Loans, net of unearned income, excluding covered loans	$ 2,478,581	$ 2,374,921
Total loans, percentage	12.00%	14.00%
Premium finance receivables | Life insurance
Loans [Line Items]
Loans, net of unearned income, excluding covered loans	$ 3,470,027	$ 2,961,496
Total loans, percentage	18.00%	17.00%
Consumer and other
Loans [Line Items]
Loans, net of unearned income, excluding covered loans	$ 122,041	$ 146,376
Total loans, percentage	1.00%	1.00%