Loans and Leases (Composition of the Loans and Leases Outstanding By Credit Quality Indicator) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans	$ 32,349,266	$ 28,322,780
Past due loans	249,119	272,770
Current loans	32,596,025	28,608,726
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans	22,613,932	18,552,002
Commercial | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		12,282,635
Commercial | Other commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		542,028
Commercial | Commercial and industrial and leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans	4,797,344	4,403,792
Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		310,093
Commercial | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans	1,054,186	1,013,454
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans	9,735,334	9,770,778
Consumer | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans	347,850	357,385
Consumer | Revolving mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		2,339,072
Consumer | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		1,780,404
Non-PCI Loans | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		18,552,002
Past due loans		74,146
Current loans		18,477,856
Non-PCI Loans | Commercial | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		12,282,635
Past due loans	35,261	37,482
Current loans	10,648,561	12,245,153
Non-PCI Loans | Commercial | Other commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		542,028
Past due loans	23,906	1,890
Current loans	2,941,998	540,138
Non-PCI Loans | Commercial | Commercial and industrial and leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		4,403,792
Past due loans	16,183	28,143
Current loans	4,781,161	4,375,649
Non-PCI Loans | Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		310,093
Past due loans	84,712	588
Current loans	22,529,220	309,505
Non-PCI Loans | Commercial | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		1,013,454
Past due loans	9,362	6,043
Current loans	1,044,824	1,007,411
Non-PCI Loans | Commercial | Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		18,157,655
Non-PCI Loans | Commercial | Pass | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		12,050,799
Non-PCI Loans | Commercial | Pass | Other commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		536,682
Non-PCI Loans | Commercial | Pass | Commercial and industrial and leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		4,256,456
Non-PCI Loans | Commercial | Pass | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		308,796
Non-PCI Loans | Commercial | Pass | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		1,004,922
Non-PCI Loans | Commercial | Special Mention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		166,866
Non-PCI Loans | Commercial | Special Mention | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		115,164
Non-PCI Loans | Commercial | Special Mention | Other commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		3,899
Non-PCI Loans | Commercial | Special Mention | Commercial and industrial and leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		44,604
Non-PCI Loans | Commercial | Special Mention | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		622
Non-PCI Loans | Commercial | Special Mention | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		2,577
Non-PCI Loans | Commercial | Substandard
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		158,897
Non-PCI Loans | Commercial | Substandard | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		116,672
Non-PCI Loans | Commercial | Substandard | Other commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		1,447
Non-PCI Loans | Commercial | Substandard | Commercial and industrial and leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		34,148
Non-PCI Loans | Commercial | Substandard | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		675
Non-PCI Loans | Commercial | Substandard | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		5,955
Non-PCI Loans | Commercial | Doubtful
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		3
Non-PCI Loans | Commercial | Doubtful | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		0
Non-PCI Loans | Commercial | Doubtful | Other commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		0
Non-PCI Loans | Commercial | Doubtful | Commercial and industrial and leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		3
Non-PCI Loans | Commercial | Doubtful | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		0
Non-PCI Loans | Commercial | Doubtful | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		0
Non-PCI Loans | Commercial | Ungraded
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		68,581
Non-PCI Loans | Commercial | Ungraded | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		0
Non-PCI Loans | Commercial | Ungraded | Other commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		0
Non-PCI Loans | Commercial | Ungraded | Commercial and industrial and leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		68,581
Non-PCI Loans | Commercial | Ungraded | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		0
Non-PCI Loans | Commercial | Ungraded | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		0
Non-PCI Loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		9,770,778
Past due loans	112,470	132,389
Current loans	9,622,864	9,638,389
Non-PCI Loans | Consumer | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		5,293,917
Past due loans		88,537
Current loans		5,205,380
Non-PCI Loans | Consumer | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		357,385
Past due loans	6,214	2,992
Current loans	1,227,982	354,393
Non-PCI Loans | Consumer | Revolving mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		2,339,072
Past due loans	1,235	23,062
Current loans	346,615	2,316,010
Non-PCI Loans | Consumer | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		1,780,404
Past due loans	7,281	17,798
Current loans	536,855	1,762,606
PCD Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	51,937	66,235
Current loans	443,941	492,481
PCD Loans | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		284,329
PCD Loans | Commercial | Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		148,412
PCD Loans | Commercial | Special Mention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		44,290
PCD Loans | Commercial | Substandard
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		87,970
PCD Loans | Commercial | Doubtful
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		3,657
PCD Loans | Commercial | Ungraded
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		0
PCD Loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		274,387
Current loans		240,995
30 to 59 Days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	121,823	136,220
30 to 59 Days past due | Non-PCI Loans | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans		42,716
30 to 59 Days past due | Non-PCI Loans | Commercial | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	23,354	20,389
30 to 59 Days past due | Non-PCI Loans | Commercial | Other commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	9,854	861
30 to 59 Days past due | Non-PCI Loans | Commercial | Commercial and industrial and leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	8,401	18,269
30 to 59 Days past due | Non-PCI Loans | Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	49,469	51
30 to 59 Days past due | Non-PCI Loans | Commercial | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	7,860	3,146
30 to 59 Days past due | Non-PCI Loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	56,056	67,026
30 to 59 Days past due | Non-PCI Loans | Consumer | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans		45,839
30 to 59 Days past due | Non-PCI Loans | Consumer | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	4,245	977
30 to 59 Days past due | Non-PCI Loans | Consumer | Revolving mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	923	9,729
30 to 59 Days past due | Non-PCI Loans | Consumer | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	4,490	10,481
30 to 59 Days past due | PCD Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	16,298	26,478
30 to 59 Days past due | PCD Loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans		13,764
60 to 89 Days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	29,490	51,058
60 to 89 Days past due | Non-PCI Loans | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans		14,553
60 to 89 Days past due | Non-PCI Loans | Commercial | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	5,212	8,774
60 to 89 Days past due | Non-PCI Loans | Commercial | Other commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	7,381	331
60 to 89 Days past due | Non-PCI Loans | Commercial | Commercial and industrial and leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	3,920	4,842
60 to 89 Days past due | Non-PCI Loans | Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	16,513	411
60 to 89 Days past due | Non-PCI Loans | Commercial | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	0	195
60 to 89 Days past due | Non-PCI Loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	9,776	25,721
60 to 89 Days past due | Non-PCI Loans | Consumer | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans		18,289
60 to 89 Days past due | Non-PCI Loans | Consumer | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	1,059	218
60 to 89 Days past due | Non-PCI Loans | Consumer | Revolving mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	0	3,468
60 to 89 Days past due | Non-PCI Loans | Consumer | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	1,324	3,746
60 to 89 Days past due | PCD Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	3,201	10,784
60 to 89 Days past due | PCD Loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans		5,608
90 Days or greater
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	97,806	85,492
90 Days or greater | Non-PCI Loans | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans		16,877
90 Days or greater | Non-PCI Loans | Commercial | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	6,695	8,319
90 Days or greater | Non-PCI Loans | Commercial | Other commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	6,671	698
90 Days or greater | Non-PCI Loans | Commercial | Commercial and industrial and leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	3,862	5,032
90 Days or greater | Non-PCI Loans | Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	18,730	126
90 Days or greater | Non-PCI Loans | Commercial | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	1,502	2,702
90 Days or greater | Non-PCI Loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	46,638	39,642
90 Days or greater | Non-PCI Loans | Consumer | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans		24,409
90 Days or greater | Non-PCI Loans | Consumer | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	910	1,797
90 Days or greater | Non-PCI Loans | Consumer | Revolving mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	312	9,865
90 Days or greater | Non-PCI Loans | Consumer | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	1,467	3,571
90 Days or greater | PCD Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	$ 32,438	28,973
90 Days or greater | PCD Loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans		$ 14,020