Loans (Credit Quality Indicators by Segments and Portfolio Class) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 16,752,151	$ 15,703,314
Total Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	12,545,507	11,560,325
Total Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	10,925,611	10,577,368
Total Commercial [Member] | Pass-Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	351,888	221,911
Total Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	248,696	270,579
Total Commercial [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,001,599	490,407
Total Commercial [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	17,713	60
Residential Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,146,713	2,049,524
Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,059,931	2,093,465
Residential Mortgage and Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,206,644	4,142,989
Commercial Real Estate - Income Producing [Member] | Total Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,013,890	1,553,082
Investor Real Estate [Member] | Total Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,013,890	1,553,082
Investor Real Estate [Member] | Total Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,873,644	1,502,484
Investor Real Estate [Member] | Total Commercial [Member] | Pass-Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	78,309	14,717
Investor Real Estate [Member] | Total Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	22,492	5,905
Investor Real Estate [Member] | Total Commercial [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	39,434	29,960
Investor Real Estate [Member] | Total Commercial [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	11	16
Construction and Land Development [Member] | Total Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,010,879	1,151,950
Construction and Land Development [Member] | Total Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	968,505	1,095,296
Construction and Land Development [Member] | Total Commercial [Member] | Pass-Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	22,592	6,841
Construction and Land Development [Member] | Total Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,142	12,297
Construction and Land Development [Member] | Total Commercial [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	15,640	37,516
Total Commercial & Industrial [Member] | Total Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	9,520,738	8,855,293
Total Commercial & Industrial [Member] | Total Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	8,083,462	7,979,588
Total Commercial & Industrial [Member] | Total Commercial [Member] | Pass-Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	250,987	200,353
Total Commercial & Industrial [Member] | Total Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	222,062	252,377
Total Commercial & Industrial [Member] | Total Commercial [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	946,525	422,931
Total Commercial & Industrial [Member] | Total Commercial [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	17,702	44
Total Commercial & Industrial [Member] | Commercial Non-Real Estate [Member] | Total Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	7,613,917	6,995,824
Total Commercial & Industrial [Member] | Commercial Non-Real Estate [Member] | Total Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	6,364,348	6,260,863
Total Commercial & Industrial [Member] | Commercial Non-Real Estate [Member] | Total Commercial [Member] | Pass-Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	203,311	168,589
Total Commercial & Industrial [Member] | Commercial Non-Real Estate [Member] | Total Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	181,763	211,230
Total Commercial & Industrial [Member] | Commercial Non-Real Estate [Member] | Total Commercial [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	846,793	355,098
Total Commercial & Industrial [Member] | Commercial Non-Real Estate [Member] | Total Commercial [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	17,702	44
Total Commercial & Industrial [Member] | Commercial Real Estate - Owner Occupied [Member] | Total Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,906,821	1,859,469
Total Commercial & Industrial [Member] | Commercial Real Estate - Owner Occupied [Member] | Total Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,719,114	1,718,725
Total Commercial & Industrial [Member] | Commercial Real Estate - Owner Occupied [Member] | Total Commercial [Member] | Pass-Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	47,676	31,764
Total Commercial & Industrial [Member] | Commercial Real Estate - Owner Occupied [Member] | Total Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	40,299	41,147
Total Commercial & Industrial [Member] | Commercial Real Estate - Owner Occupied [Member] | Total Commercial [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	99,732	67,833
Performing [Member] | Residential Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,123,048	2,025,563
Performing [Member] | Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,046,757	2,082,238
Performing [Member] | Residential Mortgage and Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,169,805	4,107,801
Nonperforming [Member] | Residential Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	23,665	23,961
Nonperforming [Member] | Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	13,174	11,227
Nonperforming [Member] | Residential Mortgage and Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 36,839	$ 35,188