Loans and Allowance for Loan Losses (Loans, Net of Unearned Income) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 15,978,124	$ 15,703,314	$ 13,924,386
Commercial Non-Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	7,145,406	6,995,824	5,987,084
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	3,676,092	3,412,551	3,150,103
Residential Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,000,967	2,049,524	1,913,885
Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,060,245	2,093,465	1,759,804
Originated Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	15,567,288	15,258,587	12,920,530
Originated Loans [Member] | Commercial Non-Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	7,088,146	6,930,453	5,861,887
Originated Loans [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	3,504,803	3,220,509	2,492,351
Originated Loans [Member] | Residential Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,839,889	1,887,256	1,736,033
Originated Loans [Member] | Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,048,068	2,080,626	1,742,810
Acquired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	211,620	241,430	765,324
Acquired Loans [Member] | Commercial Non-Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	51,949	59,843	118,260
Acquired Loans [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	156,285	176,460	629,975
Acquired Loans [Member] | Residential Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,116	27	2,485
Acquired Loans [Member] | Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	20	20	25
FDIC Acquired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	199,216	203,297	238,532
FDIC Acquired Loans [Member] | Commercial Non-Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	5,311	5,528	6,937
FDIC Acquired Loans [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	15,004	15,582	27,777
FDIC Acquired Loans [Member] | Residential Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	159,962	162,241	175,367
FDIC Acquired Loans [Member] | Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	12,157	12,819	16,969
Construction and Land Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,095,414	1,151,950	1,113,510
Construction and Land Development [Member] | Originated Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,086,382	1,139,743	1,087,449
Construction and Land Development [Member] | Acquired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,250	5,080	14,579
Construction and Land Development [Member] | FDIC Acquired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 6,782	$ 7,127	$ 11,482