Loans (Summary of Loan Portfolio) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Loans [Line Items]
Loans, net of unearned income	$ 26,800,290	$ 23,820,691
Loans, net of unearned income (as a percent)	100.00%	100.00%
Commercial
Loans [Line Items]
Loans, net of unearned income	$ 8,285,920	$ 7,828,538
Loans, net of unearned income (as a percent)	31.00%	33.00%
Commercial real estate
Loans [Line Items]
Loans, net of unearned income	$ 8,020,276	$ 6,933,252
Loans, net of unearned income (as a percent)	30.00%	29.00%
Home equity
Loans [Line Items]
Loans, net of unearned income	$ 513,066	$ 552,343
Loans, net of unearned income (as a percent)	2.00%	2.00%
Residential real estate
Loans [Line Items]
Loans, net of unearned income	$ 1,354,221	$ 1,002,464
Loans, net of unearned income (as a percent)	5.00%	4.00%
Premium finance receivables | Commercial
Loans [Line Items]
Loans, net of unearned income	$ 3,442,027	$ 2,841,659
Loans, net of unearned income (as a percent)	13.00%	12.00%
Premium finance receivables | Life insurance
Loans [Line Items]
Loans, net of unearned income	$ 5,074,602	$ 4,541,794
Loans, net of unearned income (as a percent)	19.00%	19.00%
Consumer and other
Loans [Line Items]
Loans, net of unearned income	$ 110,178	$ 120,641
Loans, net of unearned income (as a percent)	0.00%	1.00%