Loans And Allowance For Loan Losses (Loan Portfolio Credit Exposure) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 25,970,716	$ 24,812,795	$ 23,882,382
Performing, accrual of interest	172,300	190,600
Deferred fees and costs, net	24,143	25,331	$ 26,000
Total commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans	12,781,206	12,023,650
Total commercial and industrial | Commercial, financial, and agricultural
Financing Receivable, Recorded Investment [Line Items]
Total loans	7,449,698	7,179,487
Total commercial and industrial | Owner-occupied
Financing Receivable, Recorded Investment [Line Items]
Total loans	5,331,508	4,844,163
Total commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	6,564,491	6,935,288
Total commercial real estate | Investment properties
Financing Receivable, Recorded Investment [Line Items]
Total loans	5,560,951	5,670,065
Total commercial real estate | 1-4 family properties
Financing Receivable, Recorded Investment [Line Items]
Total loans	679,870	781,619
Total commercial real estate | Land and development
Financing Receivable, Recorded Investment [Line Items]
Total loans	323,670	483,604
Total consumer
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 6,625,019	5,853,857
Allowance for loan and lease losses, percent of loan amount	50.00%
Total consumer | Consumer mortgages
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 2,934,235	2,633,503
Total consumer | Home equity lines
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,515,796	1,514,227
Total consumer | Credit cards
Financing Receivable, Recorded Investment [Line Items]
Total loans	258,245	232,676
Total consumer | Other consumer loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,916,743	1,473,451
Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	25,458,715	24,222,726
Pass | Total commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans	12,402,990	11,643,383
Pass | Total commercial and industrial | Commercial, financial, and agricultural
Financing Receivable, Recorded Investment [Line Items]
Total loans	7,190,517	6,929,506
Pass | Total commercial and industrial | Owner-occupied
Financing Receivable, Recorded Investment [Line Items]
Total loans	5,212,473	4,713,877
Pass | Total commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	6,458,891	6,763,850
Pass | Total commercial real estate | Investment properties
Financing Receivable, Recorded Investment [Line Items]
Total loans	5,497,344	5,586,792
Pass | Total commercial real estate | 1-4 family properties
Financing Receivable, Recorded Investment [Line Items]
Total loans	663,692	745,299
Pass | Total commercial real estate | Land and development
Financing Receivable, Recorded Investment [Line Items]
Total loans	297,855	431,759
Pass | Total consumer
Financing Receivable, Recorded Investment [Line Items]
Total loans	6,596,834	5,815,493
Pass | Total consumer | Consumer mortgages
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,926,712	2,622,499
Pass | Total consumer | Home equity lines
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,501,316	1,491,105
Pass | Total consumer | Credit cards
Financing Receivable, Recorded Investment [Line Items]
Total loans	255,904	230,945
Pass | Total consumer | Other consumer loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,912,902	1,470,944
Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	232,952	283,865
Special Mention | Total commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans	173,226	166,052
Special Mention | Total commercial and industrial | Commercial, financial, and agricultural
Financing Receivable, Recorded Investment [Line Items]
Total loans	118,188	115,912
Special Mention | Total commercial and industrial | Owner-occupied
Financing Receivable, Recorded Investment [Line Items]
Total loans	55,038	50,140
Special Mention | Total commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	59,726	117,813
Special Mention | Total commercial real estate | Investment properties
Financing Receivable, Recorded Investment [Line Items]
Total loans	40,516	64,628
Special Mention | Total commercial real estate | 1-4 family properties
Financing Receivable, Recorded Investment [Line Items]
Total loans	6,424	19,419
Special Mention | Total commercial real estate | Land and development
Financing Receivable, Recorded Investment [Line Items]
Total loans	12,786	33,766
Special Mention | Total consumer
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Special Mention | Total consumer | Consumer mortgages
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Special Mention | Total consumer | Home equity lines
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Special Mention | Total consumer | Credit cards
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Special Mention | Total consumer | Other consumer loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	274,918	297,640
Substandard | Total commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans	203,790	212,891
Substandard | Total commercial and industrial | Commercial, financial, and agricultural
Financing Receivable, Recorded Investment [Line Items]
Total loans	140,218	132,818
Substandard | Total commercial and industrial | Owner-occupied
Financing Receivable, Recorded Investment [Line Items]
Total loans	63,572	80,073
Substandard | Total commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	45,874	50,496
Substandard | Total commercial real estate | Investment properties
Financing Receivable, Recorded Investment [Line Items]
Total loans	23,091	18,645
Substandard | Total commercial real estate | 1-4 family properties
Financing Receivable, Recorded Investment [Line Items]
Total loans	9,754	16,901
Substandard | Total commercial real estate | Land and development
Financing Receivable, Recorded Investment [Line Items]
Total loans	13,029	14,950
Substandard | Total consumer
Financing Receivable, Recorded Investment [Line Items]
Total loans	25,254	34,253
Substandard | Total consumer | Consumer mortgages
Financing Receivable, Recorded Investment [Line Items]
Total loans	7,425	10,607
Substandard | Total consumer | Home equity lines
Financing Receivable, Recorded Investment [Line Items]
Total loans	13,130	21,079
Substandard | Total consumer | Credit cards
Financing Receivable, Recorded Investment [Line Items]
Total loans	858	399
Substandard | Total consumer | Other consumer loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,841	2,168
Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,472	5,358
Doubtful | Total commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,200	1,324
Doubtful | Total commercial and industrial | Commercial, financial, and agricultural
Financing Receivable, Recorded Investment [Line Items]
Total loans	775	1,251
Doubtful | Total commercial and industrial | Owner-occupied
Financing Receivable, Recorded Investment [Line Items]
Total loans	425	73
Doubtful | Total commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	3,129
Doubtful | Total commercial real estate | Investment properties
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Doubtful | Total commercial real estate | 1-4 family properties
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Doubtful | Total commercial real estate | Land and development
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	3,129
Doubtful | Total consumer
Financing Receivable, Recorded Investment [Line Items]
Total loans	272	905
Doubtful | Total consumer | Consumer mortgages
Financing Receivable, Recorded Investment [Line Items]
Total loans	98	291
Doubtful | Total consumer | Home equity lines
Financing Receivable, Recorded Investment [Line Items]
Total loans	174	285
Doubtful | Total consumer | Credit cards
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Doubtful | Total consumer | Other consumer loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	329
Loss
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,659	3,206
Loss | Total commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Loss | Total commercial and industrial | Commercial, financial, and agricultural
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Loss | Total commercial and industrial | Owner-occupied
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Loss | Total commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Loss | Total commercial real estate | Investment properties
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Loss | Total commercial real estate | 1-4 family properties
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Loss | Total commercial real estate | Land and development
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Loss | Total consumer
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,659	3,206
Loss | Total consumer | Consumer mortgages
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	106
Loss | Total consumer | Home equity lines
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,176	1,758
Loss | Total consumer | Credit cards
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,483	1,332
Loss | Total consumer | Other consumer loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 0	$ 10