Loans and Allowance for Loan Losses (Credit Quality Indicators of Various Classes of Loans) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 15,978,124	$ 15,703,314	$ 13,924,386
Originated Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	15,567,288	15,258,587	12,920,530
Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	211,620	241,430	765,324
FDIC Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	199,216	203,297	238,532
Commercial Non-Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	7,145,406	6,995,824	5,987,084
Commercial Non-Real Estate [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	7,088,146	6,930,453	5,861,887
Commercial Non-Real Estate [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	51,949	59,843	118,260
Commercial Non-Real Estate [Member] | FDIC Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	5,311	5,528	6,937
Commercial Non-Real Estate [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	5,942,564	6,260,863
Commercial Non-Real Estate [Member] | Pass [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	5,895,649	6,205,372
Commercial Non-Real Estate [Member] | Pass [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	44,847	53,381
Commercial Non-Real Estate [Member] | Pass [Member] | FDIC Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,068	2,110
Commercial Non-Real Estate [Member] | Pass-Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	298,909	168,589
Commercial Non-Real Estate [Member] | Pass-Watch [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	298,176	167,720
Commercial Non-Real Estate [Member] | Pass-Watch [Member] | FDIC Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	733	869
Commercial Non-Real Estate [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	208,733	211,230
Commercial Non-Real Estate [Member] | Special Mention [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	208,731	211,230
Commercial Non-Real Estate [Member] | Special Mention [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	2
Commercial Non-Real Estate [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	693,059	355,098
Commercial Non-Real Estate [Member] | Substandard [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	683,449	346,087
Commercial Non-Real Estate [Member] | Substandard [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	7,100	6,462
Commercial Non-Real Estate [Member] | Substandard [Member] | FDIC Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,510	2,549
Commercial Non-Real Estate [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,141	44
Commercial Non-Real Estate [Member] | Doubtful [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,141	44
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,676,092	3,412,551	3,150,103
Commercial Real Estate [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,504,803	3,220,509	2,492,351
Commercial Real Estate [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	156,285	176,460	629,975
Commercial Real Estate [Member] | FDIC Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	15,004	15,582	27,777
Commercial Real Estate [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,433,845	3,221,209
Commercial Real Estate [Member] | Pass [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,293,852	3,058,342
Commercial Real Estate [Member] | Pass [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	136,879	159,750
Commercial Real Estate [Member] | Pass [Member] | FDIC Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,114	3,117
Commercial Real Estate [Member] | Pass-Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	64,512	46,481
Commercial Real Estate [Member] | Pass-Watch [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	60,595	41,830
Commercial Real Estate [Member] | Pass-Watch [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,684	2,355
Commercial Real Estate [Member] | Pass-Watch [Member] | FDIC Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,233	2,296
Commercial Real Estate [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	48,117	47,052
Commercial Real Estate [Member] | Special Mention [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	42,170	40,576
Commercial Real Estate [Member] | Special Mention [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,804	5,112
Commercial Real Estate [Member] | Special Mention [Member] | FDIC Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,143	1,364
Commercial Real Estate [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	129,603	97,793
Commercial Real Estate [Member] | Substandard [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	108,171	79,745
Commercial Real Estate [Member] | Substandard [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	12,918	9,243
Commercial Real Estate [Member] | Substandard [Member] | FDIC Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	8,514	8,805
Commercial Real Estate [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	15	16
Commercial Real Estate [Member] | Doubtful [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	15	16
Residential Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,000,967	2,049,524	1,913,885
Residential Mortgages [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,839,889	1,887,256	1,736,033
Residential Mortgages [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,116	27	2,485
Residential Mortgages [Member] | FDIC Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	159,962	162,241	175,367
Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,060,245	2,093,465	1,759,804
Consumer [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,048,068	2,080,626	1,742,810
Consumer [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	20	20	25
Consumer [Member] | FDIC Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	12,157	12,819	16,969
Construction and Land Development [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,095,414	1,151,950	1,113,510
Construction and Land Development [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,086,382	1,139,743	1,087,449
Construction and Land Development [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,250	5,080	14,579
Construction and Land Development [Member] | FDIC Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	6,782	7,127	$ 11,482
Construction and Land Development [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,039,139	1,095,296
Construction and Land Development [Member] | Pass [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,036,847	1,092,299
Construction and Land Development [Member] | Pass [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	837	910
Construction and Land Development [Member] | Pass [Member] | FDIC Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,455	2,087
Construction and Land Development [Member] | Pass-Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	24,982	6,841
Construction and Land Development [Member] | Pass-Watch [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	22,947	5,709
Construction and Land Development [Member] | Pass-Watch [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	150	223
Construction and Land Development [Member] | Pass-Watch [Member] | FDIC Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,885	909
Construction and Land Development [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	613	12,297
Construction and Land Development [Member] | Special Mention [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	592	12,017
Construction and Land Development [Member] | Special Mention [Member] | FDIC Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	21	280
Construction and Land Development [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	30,680	37,516
Construction and Land Development [Member] | Substandard [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	25,996	29,718
Construction and Land Development [Member] | Substandard [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,263	3,947
Construction and Land Development [Member] | Substandard [Member] | FDIC Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,421	3,851
Performing [Member] | Residential Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,977,131	2,025,563
Performing [Member] | Residential Mortgages [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,816,053	1,863,295
Performing [Member] | Residential Mortgages [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,116	27
Performing [Member] | Residential Mortgages [Member] | FDIC Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	159,962	162,241
Performing [Member] | Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,050,609	2,082,238
Performing [Member] | Consumer [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,038,432	2,069,399
Performing [Member] | Consumer [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	20	20
Performing [Member] | Consumer [Member] | FDIC Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	12,157	12,819
Nonperforming [Member] | Residential Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	23,836	23,961
Nonperforming [Member] | Residential Mortgages [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	23,836	23,961
Nonperforming [Member] | Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	9,636	11,227
Nonperforming [Member] | Consumer [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 9,636	$ 11,227