Loans and Allowance for Loan Losses (Loans, Net of Unearned Income) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 18,473,841	$ 16,752,151	$ 16,035,796
Total Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	13,886,631	12,545,507
Residential Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,493,923	2,146,713	2,017,650
Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,093,287	2,059,931	2,064,368
Commercial Real Estate - Income Producing [Member] | Total Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,401,673	2,013,890	2,024,471
Construction and Land Development [Member] | Total Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,313,522	1,010,879	880,588
Total Commercial & Industrial [Member] | Total Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	10,171,436	9,520,738	9,048,719
Total Commercial & Industrial [Member] | Commercial Non-Real Estate [Member] | Total Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	8,093,104	7,613,917	7,132,519
Total Commercial & Industrial [Member] | Commercial Real Estate - Owner Occupied [Member] | Total Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 2,078,332	$ 1,906,821	$ 1,916,200