Loans and Allowance for Loan Losses (Schedule Of Current, Accruing Past Due And Nonaccrual Loans) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	$ 24,732,767	$ 24,645,203
Accruing 30-89 Days Past Due	48,734	47,617
Accruing 90 Days or Greater Past Due	5,416	4,414
Total Accruing Past Due	54,150	52,031
Non-accrual	120,081	115,561
Total loans	24,906,998	24,812,795	$ 24,284,188
Deferred fees and costs, net	24,000	25,300	$ 25,700
Total commercial real estate
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	6,816,766	6,914,819
Accruing 30-89 Days Past Due	7,668	7,660
Accruing 90 Days or Greater Past Due	1,155	359
Total Accruing Past Due	8,823	8,019
Non-accrual	10,138	12,450
Total loans	6,835,727	6,935,288
Total commercial real estate | Investment properties
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	5,613,811	5,663,665
Accruing 30-89 Days Past Due	1,986	2,506
Accruing 90 Days or Greater Past Due	323	90
Total Accruing Past Due	2,309	2,596
Non-accrual	2,930	3,804
Total loans	5,619,050	5,670,065
Total commercial real estate | 1-4 family properties
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	753,255	775,023
Accruing 30-89 Days Past Due	2,232	3,545
Accruing 90 Days or Greater Past Due	783	202
Total Accruing Past Due	3,015	3,747
Non-accrual	2,634	2,849
Total loans	758,904	781,619
Total commercial real estate | Land and development
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	449,700	476,131
Accruing 30-89 Days Past Due	3,450	1,609
Accruing 90 Days or Greater Past Due	49	67
Total Accruing Past Due	3,499	1,676
Non-accrual	4,574	5,797
Total loans	457,773	483,604
Total commercial and industrial
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	11,994,812	11,927,277
Accruing 30-89 Days Past Due	19,713	18,094
Accruing 90 Days or Greater Past Due	1,719	1,495
Total Accruing Past Due	21,432	19,589
Non-accrual	85,673	76,784
Total loans	12,101,917	12,023,650
Total commercial and industrial | Commercial, financial and agricultural
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	7,093,270	7,097,127
Accruing 30-89 Days Past Due	15,872	11,214
Accruing 90 Days or Greater Past Due	783	1,016
Total Accruing Past Due	16,655	12,230
Non-accrual	81,606	70,130
Total loans	7,191,531	7,179,487
Total commercial and industrial | Owner-occupied
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	4,901,542	4,830,150
Accruing 30-89 Days Past Due	3,841	6,880
Accruing 90 Days or Greater Past Due	936	479
Total Accruing Past Due	4,777	7,359
Non-accrual	4,067	6,654
Total loans	4,910,386	4,844,163
Total consumer
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	5,921,189	5,803,107
Accruing 30-89 Days Past Due	21,353	21,863
Accruing 90 Days or Greater Past Due	2,542	2,560
Total Accruing Past Due	23,895	24,423
Non-accrual	24,270	26,327
Total loans	5,969,354	5,853,857
Total consumer | Home equity lines
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	1,450,454	1,490,808
Accruing 30-89 Days Past Due	6,718	5,629
Accruing 90 Days or Greater Past Due	431	335
Total Accruing Past Due	7,149	5,964
Non-accrual	14,868	17,455
Total loans	1,472,471	1,514,227
Total consumer | Consumer mortgages
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	2,651,758	2,622,061
Accruing 30-89 Days Past Due	3,905	3,971
Accruing 90 Days or Greater Past Due	0	268
Total Accruing Past Due	3,905	4,239
Non-accrual	7,708	7,203
Total loans	2,663,371	2,633,503
Total consumer | Credit cards
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	223,232	229,015
Accruing 30-89 Days Past Due	1,599	1,930
Accruing 90 Days or Greater Past Due	1,882	1,731
Total Accruing Past Due	3,481	3,661
Non-accrual	0	0
Total loans	226,713	232,676
Total consumer | Other consumer loans
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	1,595,745	1,461,223
Accruing 30-89 Days Past Due	9,131	10,333
Accruing 90 Days or Greater Past Due	229	226
Total Accruing Past Due	9,360	10,559
Non-accrual	1,694	1,669
Total loans	$ 1,606,799	$ 1,473,451