Loans and Allowance for Loan Losses (Loans, Net of Unearned Income) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 16,070,821	$ 15,703,314	$ 14,763,050
Total Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	11,972,654	11,560,325
Residential Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,037,162	2,049,524	2,013,789
Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,061,005	2,093,465	1,990,296
Commercial Real Estate - Income Producing [Member] | Total Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,990,309	1,553,082	1,484,232
Construction and Land Development [Member] | Total Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	946,592	1,151,950	1,085,585
Total Commercial & Industrial [Member] | Total Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	9,035,753	8,855,293	8,189,148
Total Commercial & Industrial [Member] | Commercial Non-Real Estate [Member] | Total Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	7,133,928	6,995,824	6,345,994
Total Commercial & Industrial [Member] | Commercial Real Estate - Owner Occupied [Member] | Total Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 1,901,825	$ 1,859,469	$ 1,843,154