Loans and Allowance for Loan Losses (Schedule Of Current, Accruing Past Due And Nonaccrual Loans) (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	$ 24,063,685	$ 23,663,898
Accruing 30-89 Days Past Due	59,360	61,971
Accruing 90 Days or Greater Past Due	2,777	3,135
Total Accruing Past Due	62,137	65,106
Non-accrual	158,366	153,378
Total loans	24,284,188	23,882,382	$ 22,787,534
Deferred fees and costs, net	25,700	26,000	$ 29,300
Commercial Real Estate [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	7,416,919	7,326,161
Accruing 30-89 Days Past Due	15,739	9,037
Accruing 90 Days or Greater Past Due	370	161
Total Accruing Past Due	16,109	9,198
Non-accrual	26,195	30,615
Total loans	7,459,223	7,365,974
Investment Properties [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	6,009,438	5,861,198
Accruing 30-89 Days Past Due	3,574	2,795
Accruing 90 Days or Greater Past Due	0	0
Total Accruing Past Due	3,574	2,795
Non-accrual	3,040	5,268
Total loans	6,016,052	5,869,261
1-4 Family Properties [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	848,034	873,231
Accruing 30-89 Days Past Due	4,136	4,801
Accruing 90 Days or Greater Past Due	298	161
Total Accruing Past Due	4,434	4,962
Non-accrual	8,803	9,114
Total loans	861,271	887,307
Land and Development [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	559,447	591,732
Accruing 30-89 Days Past Due	8,029	1,441
Accruing 90 Days or Greater Past Due	72	0
Total Accruing Past Due	8,101	1,441
Non-accrual	14,352	16,233
Total loans	581,900	609,406
Commercial and Industrial [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	11,629,269	11,447,947
Accruing 30-89 Days Past Due	23,872	27,455
Accruing 90 Days or Greater Past Due	680	964
Total Accruing Past Due	24,552	28,419
Non-accrual	86,945	75,577
Total loans	11,740,766	11,551,943
Commercial, Financial and Agricultural [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	6,978,658	6,846,591
Accruing 30-89 Days Past Due	16,313	9,542
Accruing 90 Days or Greater Past Due	680	720
Total Accruing Past Due	16,993	10,262
Non-accrual	60,381	59,074
Total loans	7,056,032	6,915,927
Owner-Occupied [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	4,650,611	4,601,356
Accruing 30-89 Days Past Due	7,559	17,913
Accruing 90 Days or Greater Past Due	0	244
Total Accruing Past Due	7,559	18,157
Non-accrual	26,564	16,503
Total loans	4,684,734	4,636,016
Retail [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	5,017,497	4,889,790
Accruing 30-89 Days Past Due	19,749	25,479
Accruing 90 Days or Greater Past Due	1,727	2,010
Total Accruing Past Due	21,476	27,489
Non-accrual	45,226	47,186
Total loans	5,084,199	4,964,465
Home Equity Lines [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	1,558,111	1,585,228
Accruing 30-89 Days Past Due	5,961	10,013
Accruing 90 Days or Greater Past Due	112	473
Total Accruing Past Due	6,073	10,486
Non-accrual	22,918	21,551
Total loans	1,587,102	1,617,265
Consumer Mortgages [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	2,323,543	2,265,966
Accruing 30-89 Days Past Due	7,313	7,876
Accruing 90 Days or Greater Past Due	0	81
Total Accruing Past Due	7,313	7,957
Non-accrual	19,874	22,681
Total loans	2,350,730	2,296,604
Credit Cards [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	221,018	229,177
Accruing 30-89 Days Past Due	1,716	1,819
Accruing 90 Days or Greater Past Due	1,615	1,417
Total Accruing Past Due	3,331	3,236
Non-accrual	0	0
Total loans	224,349	232,413
Other Consumer Loans [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	914,825	809,419
Accruing 30-89 Days Past Due	4,759	5,771
Accruing 90 Days or Greater Past Due	0	39
Total Accruing Past Due	4,759	5,810
Non-accrual	2,434	2,954
Total loans	$ 922,018	$ 818,183