Loans and Allowance for Loan Losses (Loans, Net of Unearned Income) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 16,035,796	$ 15,703,314	$ 14,344,752
Total Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	11,953,778	11,560,325
Residential Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,017,650	2,049,524	1,955,837
Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,064,368	2,093,465	1,869,451
Commercial Real Estate - Income Producing [Member] | Total Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,024,471	1,553,082	1,452,091
Construction and Land Development [Member] | Total Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	880,588	1,151,950	1,120,947
Total Commercial & Industrial [Member] | Total Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	9,048,719	8,855,293	7,946,426
Total Commercial & Industrial [Member] | Commercial Non-Real Estate [Member] | Total Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	7,132,519	6,995,824	6,185,684
Total Commercial & Industrial [Member] | Commercial Real Estate - Owner Occupied [Member] | Total Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 1,916,200	$ 1,859,469	$ 1,760,742