Loans And Allowance For Loan Losses (Loan Portfolio Credit Exposure) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 23,882,382	$ 22,459,664
Performing, accrual of interest	256,600	303,700
Deferred fees and costs, net	25,991	30,099	$ 30,800
Home Equity Lines [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,617,265	1,689,914
Consumer Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,296,604	1,938,683
Credit Cards [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	232,413	240,851
Other Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	818,183	423,318
Investment Properties [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	5,932,619	5,751,631
1-4 Family Properties [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,023,821	1,129,156
Land Acquisition [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	409,534	513,981
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	7,365,974	7,394,768
Commercial And Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	11,551,943	10,772,130
Commercial, Financial and Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	6,915,927	6,453,180
Owner-Occupied [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,636,016	4,318,950
Retail [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 4,964,465	4,292,766
Allowance for loan and lease losses, percent of loan amount	50.00%
Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 23,147,814	21,531,712
Pass [Member] | Home Equity Lines [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,589,199	1,666,586
Pass [Member] | Consumer Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,271,916	1,910,649
Pass [Member] | Credit Cards [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	230,997	239,405
Pass [Member] | Other Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	814,844	418,929
Pass [Member] | Investment Properties [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	5,843,433	5,560,595
Pass [Member] | 1-4 Family Properties [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	932,340	995,903
Pass [Member] | Land Acquisition [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	360,017	436,835
Pass [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	7,135,790	6,993,333
Pass [Member] | Commercial And Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	11,105,068	10,302,810
Pass [Member] | Commercial, Financial and Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	6,642,648	6,184,179
Pass [Member] | Owner-Occupied [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,462,420	4,118,631
Pass [Member] | Retail [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,906,956	4,235,569
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	324,593	455,917
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	54,486	114,705
Special Mention [Member] | 1-4 Family Properties [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	51,623	64,325
Special Mention [Member] | Land Acquisition [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	31,360	46,208
Special Mention [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	137,469	225,238
Special Mention [Member] | Commercial And Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	187,124	230,679
Special Mention [Member] | Commercial, Financial and Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	126,268	152,189
Special Mention [Member] | Owner-Occupied [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	60,856	78,490
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	387,117	441,853
Substandard [Member] | Home Equity Lines [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	22,774	20,456
Substandard [Member] | Consumer Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	23,268	26,041
Substandard [Member] | Credit Cards [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	637	480
Substandard [Member] | Other Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,233	4,315
Substandard [Member] | Investment Properties [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	34,700	76,331
Substandard [Member] | 1-4 Family Properties [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	32,853	61,726
Substandard [Member] | Land Acquisition [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	17,897	30,574
Substandard [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	85,450	168,631
Substandard [Member] | Commercial And Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	251,755	221,930
Substandard [Member] | Commercial, Financial and Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	140,425	100,658
Substandard [Member] | Owner-Occupied [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	111,330	121,272
Substandard [Member] | Retail [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	49,912	51,292
Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	19,337	23,900
Doubtful [Member] | Home Equity Lines [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,892	1,206
Doubtful [Member] | Consumer Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,283	1,700
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	42	0
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	7,005	7,202
Doubtful [Member] | Land Acquisition [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	260	364
Doubtful [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	7,265	7,566
Doubtful [Member] | Commercial And Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	7,855	13,428
Doubtful [Member] | Commercial, Financial and Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	6,445	13,330
Doubtful [Member] | Owner-Occupied [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,410	98
Doubtful [Member] | Retail [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,217	2,906
Loss [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,521	6,282
Loss [Member] | Home Equity Lines [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,400	1,666
Loss [Member] | Consumer Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	137	293
Loss [Member] | Credit Cards [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	779	966
Loss [Member] | Other Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	64	74
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	141	3,283
Loss [Member] | Commercial, Financial and Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	141	2,824
Loss [Member] | Owner-Occupied [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	459
Loss [Member] | Retail [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 3,380	$ 2,999