Loans and Allowance for Loan Losses (Schedule of Current, Accruing Past Due and Nonaccrual Loans) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	$ 38,236,018	$ 38,252,984
Non-accrual	136,382	127,720
Non-accrual, without an allowance	24,646	23,359
Total commercial and industrial
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	19,150,133	19,520,168
Non-accrual	62,352	75,546
Non-accrual, without an allowance	21,746	21,859
Total commercial and industrial | Commercial, financial and agricultural
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	12,085,534	12,410,152
Non-accrual	49,197	55,527
Non-accrual, without an allowance	21,746	21,859
Total commercial and industrial | Owner-occupied
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	7,064,599	7,110,016
Non-accrual	13,155	20,019
Non-accrual, without an allowance	0	0
Total commercial real estate
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	10,361,051	10,325,707
Non-accrual	6,389	28,913
Non-accrual, without an allowance	2,900	1,500
Total commercial real estate | Investment properties
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	9,218,013	9,103,379
Non-accrual	2,367	24,631
Non-accrual, without an allowance	2,407	0
Total commercial real estate | 1-4 family properties
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	636,344	628,695
Non-accrual	1,982	2,383
Non-accrual, without an allowance	493	1,236
Total commercial real estate | Land and development
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	506,694	593,633
Non-accrual	2,040	1,899
Non-accrual, without an allowance	0	264
Total consumer
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	8,724,834	8,407,109
Non-accrual	67,641	23,261
Non-accrual, without an allowance	0	0
Total consumer | Consumer mortgages
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	5,200,762	5,513,491
Non-accrual	51,376	8,740
Non-accrual, without an allowance	0	0
Total consumer | Home equity lines
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	1,358,211	1,537,726
Non-accrual	8,938	12,145
Non-accrual, without an allowance	0	0
Total consumer | Credit cards
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	285,508	281,018
Non-accrual	0	0
Non-accrual, without an allowance	0	0
Total consumer | Other consumer loans
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	1,880,353	1,074,874
Non-accrual	7,327	2,376
Non-accrual, without an allowance	0	0
Current
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	38,025,669	38,054,556
Current | Total commercial and industrial
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	19,051,210	19,409,506
Current | Total commercial and industrial | Commercial, financial and agricultural
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	12,002,589	12,321,514
Current | Total commercial and industrial | Owner-occupied
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	7,048,621	7,087,992
Current | Total commercial real estate
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	10,342,458	10,288,383
Current | Total commercial real estate | Investment properties
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	9,205,776	9,075,843
Current | Total commercial real estate | 1-4 family properties
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	632,412	621,492
Current | Total commercial real estate | Land and development
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	504,270	591,048
Current | Total consumer
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	8,632,001	8,356,667
Current | Total consumer | Consumer mortgages
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	5,144,394	5,495,415
Current | Total consumer | Home equity lines
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	1,346,562	1,521,575
Current | Total consumer | Credit cards
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	282,361	276,778
Current | Total consumer | Other consumer loans
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	1,858,684	1,062,899
Accruing 30 to 89 Days Past Due
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	44,906	43,232
Accruing 30 to 89 Days Past Due | Total commercial and industrial
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	13,148	12,169
Accruing 30 to 89 Days Past Due | Total commercial and industrial | Commercial, financial and agricultural
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	11,161	10,256
Accruing 30 to 89 Days Past Due | Total commercial and industrial | Owner-occupied
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	1,987	1,913
Accruing 30 to 89 Days Past Due | Total commercial real estate
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	8,800	6,721
Accruing 30 to 89 Days Past Due | Total commercial real estate | Investment properties
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	7,461	2,751
Accruing 30 to 89 Days Past Due | Total commercial real estate | 1-4 family properties
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	1,076	3,548
Accruing 30 to 89 Days Past Due | Total commercial real estate | Land and development
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	263	422
Accruing 30 to 89 Days Past Due | Total consumer
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	22,958	24,342
Accruing 30 to 89 Days Past Due | Total consumer | Consumer mortgages
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	4,992	8,851
Accruing 30 to 89 Days Past Due | Total consumer | Home equity lines
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	2,711	4,006
Accruing 30 to 89 Days Past Due | Total consumer | Credit cards
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	1,524	2,363
Accruing 30 to 89 Days Past Due | Total consumer | Other consumer loans
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	13,731	9,122
Accruing 90 to 149 Days Past Due
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	4,415	4,117
Accruing 90 to 149 Days Past Due | Total commercial and industrial
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	1,677	1,088
Accruing 90 to 149 Days Past Due | Total commercial and industrial | Commercial, financial and agricultural
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	841	996
Accruing 90 to 149 Days Past Due | Total commercial and industrial | Owner-occupied
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	836	92
Accruing 90 to 149 Days Past Due | Total commercial real estate
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	504	190
Accruing 90 to 149 Days Past Due | Total commercial real estate | Investment properties
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	2	154
Accruing 90 to 149 Days Past Due | Total commercial real estate | 1-4 family properties
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	381	36
Accruing 90 to 149 Days Past Due | Total commercial real estate | Land and development
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	121	0
Accruing 90 to 149 Days Past Due | Total consumer
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	2,234	2,839
Accruing 90 to 149 Days Past Due | Total consumer | Consumer mortgages
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	0	485
Accruing 90 to 149 Days Past Due | Total consumer | Home equity lines
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	0	0
Accruing 90 to 149 Days Past Due | Total consumer | Credit cards
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	1,623	1,877
Accruing 90 to 149 Days Past Due | Total consumer | Other consumer loans
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	611	477
Total Accruing Past Due
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	49,321	47,349
Total Accruing Past Due | Total commercial and industrial
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	14,825	13,257
Total Accruing Past Due | Total commercial and industrial | Commercial, financial and agricultural
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	12,002	11,252
Total Accruing Past Due | Total commercial and industrial | Owner-occupied
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	2,823	2,005
Total Accruing Past Due | Total commercial real estate
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	9,304	6,911
Total Accruing Past Due | Total commercial real estate | Investment properties
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	7,463	2,905
Total Accruing Past Due | Total commercial real estate | 1-4 family properties
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	1,457	3,584
Total Accruing Past Due | Total commercial real estate | Land and development
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	384	422
Total Accruing Past Due | Total consumer
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	25,192	27,181
Total Accruing Past Due | Total consumer | Consumer mortgages
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	4,992	9,336
Total Accruing Past Due | Total consumer | Home equity lines
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	2,711	4,006
Total Accruing Past Due | Total consumer | Credit cards
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	3,147	4,240
Total Accruing Past Due | Total consumer | Other consumer loans
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loans, net of deferred fees and costs	$ 14,342	$ 9,599