Loans And Allowance For Loan Losses (Loan Portfolio Credit Exposure) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 22,459,664	$ 21,128,489
Nonaccrual substandard loans	138,200	170,900
Deferred fees and costs, net	30,099	30,790	$ 28,900
Home Equity Lines [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,689,914	1,683,998
Consumer Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,938,683	1,694,061
Credit Cards [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	240,851	253,649
Other Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	423,318	302,460
Investment Properties [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	5,751,631	5,206,674
1-4 Family Properties [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,109,854	1,133,882
Land Acquisition [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	513,981	586,046
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	7,375,466	6,926,602
Commercial And Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	10,791,432	10,267,719
Commercial, Financial and Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	6,472,482	6,182,312
Owner-Occupied [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,318,950	4,085,407
Retail [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 4,292,766	3,934,168
Allowance for loan and lease losses, percent of loan amount	50.00%
Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 21,531,712	19,940,436
Pass [Member] | Home Equity Lines [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,666,586	1,659,794
Pass [Member] | Consumer Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,910,649	1,653,491
Pass [Member] | Credit Cards [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	239,405	252,275
Pass [Member] | Other Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	418,929	298,991
Pass [Member] | Investment Properties [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	5,560,595	4,936,319
Pass [Member] | 1-4 Family Properties [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	976,601	943,721
Pass [Member] | Land Acquisition [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	436,835	462,313
Pass [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	6,974,031	6,342,353
Pass [Member] | Commercial And Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	10,322,112	9,733,532
Pass [Member] | Commercial, Financial and Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	6,203,481	5,905,589
Pass [Member] | Owner-Occupied [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,118,631	3,827,943
Pass [Member] | Retail [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,235,569	3,864,551
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	455,917	553,990
Special Mention [Member] | Home Equity Lines [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Special Mention [Member] | Consumer Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Special Mention [Member] | Credit Cards [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Special Mention [Member] | Other Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Special Mention [Member] | Investment Properties [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	114,705	167,490
Special Mention [Member] | 1-4 Family Properties [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	64,325	86,072
Special Mention [Member] | Land Acquisition [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	46,208	60,902
Special Mention [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	225,238	314,464
Special Mention [Member] | Commercial And Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	230,679	239,526
Special Mention [Member] | Commercial, Financial and Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	152,189	143,879
Special Mention [Member] | Owner-Occupied [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	78,490	95,647
Special Mention [Member] | Retail [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	441,853	607,161
Substandard [Member] | Home Equity Lines [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	20,456	20,043
Substandard [Member] | Consumer Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	26,041	37,656
Substandard [Member] | Credit Cards [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	480	495
Substandard [Member] | Other Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,315	3,339
Substandard [Member] | Investment Properties [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	76,331	102,865
Substandard [Member] | 1-4 Family Properties [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	61,726	96,392
Substandard [Member] | Land Acquisition [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	30,574	62,101
Substandard [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	168,631	261,358
Substandard [Member] | Commercial And Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	221,930	284,270
Substandard [Member] | Commercial, Financial and Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	100,658	123,225
Substandard [Member] | Owner-Occupied [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	121,272	161,045
Substandard [Member] | Retail [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	51,292	61,533
Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	23,900	22,988
Doubtful [Member] | Home Equity Lines [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,206	2,009
Doubtful [Member] | Consumer Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,700	2,654
Doubtful [Member] | Credit Cards [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Doubtful [Member] | Other Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	32
Doubtful [Member] | Investment Properties [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Doubtful [Member] | 1-4 Family Properties [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	7,202	7,697
Doubtful [Member] | Land Acquisition [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	364	730
Doubtful [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	7,566	8,427
Doubtful [Member] | Commercial And Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	13,428	9,866
Doubtful [Member] | Commercial, Financial and Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	13,330	9,539
Doubtful [Member] | Owner-Occupied [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	98	327
Doubtful [Member] | Retail [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,906	4,695
Loss [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	6,282	3,914
Loss [Member] | Home Equity Lines [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,666	2,152
Loss [Member] | Consumer Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	293	260
Loss [Member] | Credit Cards [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	966	879
Loss [Member] | Other Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	74	98
Loss [Member] | Investment Properties [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Loss [Member] | 1-4 Family Properties [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Loss [Member] | Land Acquisition [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Loss [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Loss [Member] | Commercial And Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,283	525
Loss [Member] | Commercial, Financial and Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,824	80
Loss [Member] | Owner-Occupied [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	459	445
Loss [Member] | Retail [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 2,999	$ 3,389