Loans and Leases (Composition of the Loans and Leases Outstanding By Credit Quality Indicator) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans	$ 28,680,607	$ 28,322,780
Past due loans	277,651	206,535
Current loans	28,963,308	28,116,245
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans	18,886,482	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	4,738,098	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	1,014,017	1,013,454
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans	9,794,125	9,770,778
Consumer | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans	363,190	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	40,375	37,482
Current loans	10,035,757	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	14,376	1,890
Current loans	3,043,859	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	29,250	28,143
Current loans	4,708,848	4,375,649
Non-PCI Loans | Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI loans		310,093
Past due loans	89,738	588
Current loans	18,796,744	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	5,737	6,043
Current loans	1,008,280	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	123,644	132,389
Current loans	9,670,481	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	8,341	2,992
Current loans	1,192,811	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	7,645	23,062
Current loans	355,545	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	7,998	17,798
Current loans	559,729	1,762,606
PCD Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	64,269
Current loans	496,083
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	146,672	109,742
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	22,793	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	9,173	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	18,076	18,269
30 to 59 Days past due | Non-PCI Loans | Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	53,339	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	3,297	3,146
30 to 59 Days past due | Non-PCI Loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	65,705	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	5,675	977
30 to 59 Days past due | Non-PCI Loans | Consumer | Revolving mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	6,089	9,729
30 to 59 Days past due | Non-PCI Loans | Consumer | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	3,647	10,481
30 to 59 Days past due | PCD Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	27,628
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	34,001	40,274
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	3,083	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	308	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	6,924	4,842
60 to 89 Days past due | Non-PCI Loans | Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	10,657	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	342	195
60 to 89 Days past due | Non-PCI Loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	14,664	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	1,181	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	2,058	3,746
60 to 89 Days past due | PCD Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	8,680
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	96,978	56,519
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	14,499	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	4,895	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	4,250	5,032
90 Days or greater | Non-PCI Loans | Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	25,742	126
90 Days or greater | Non-PCI Loans | Commercial | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	2,098	2,702
90 Days or greater | Non-PCI Loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	43,275	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	1,485	1,797
90 Days or greater | Non-PCI Loans | Consumer | Revolving mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	1,556	9,865
90 Days or greater | Non-PCI Loans | Consumer | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	2,293	3,571
90 Days or greater | PCD Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans	$ 27,961
90 Days or greater | PCD Loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loans		$ 14,020