Loans and Allowance for Credit Losses Past Due Loan Status and Non-Accrual Loans by Portfolio Segment (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	$ 212,342	$ 208,371
≥ 90 Days Past Due and Accruing	11,689	11,106
Non- accrual	124,287	128,572
Current	16,474,524	15,957,429
Loans and leases, net of unearned income	16,686,866	16,165,800	$ 15,925,093
Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	60,637	53,640
Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	15,729	15,053
Real-estate - commercial mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	75,102	45,859
≥ 90 Days Past Due and Accruing	1,301	1,765
Non- accrual	44,409	30,388
Current	6,529,532	6,388,426
Loans and leases, net of unearned income	6,604,634	6,434,285	6,337,984
Real-estate - commercial mortgage | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	25,100	12,206
Real-estate - commercial mortgage | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	4,292	1,500
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	41,590	56,532
≥ 90 Days Past Due and Accruing	731	1,068
Non- accrual	35,664	49,299
Current	4,268,442	4,168,448
Loans and leases, net of unearned income	4,310,032	4,224,980
Commercial | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	3,234	5,227
Commercial | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	1,961	938
Commercial - unsecured
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	907	2,500
≥ 90 Days Past Due and Accruing	153	51
Non- accrual	578	851
Current	183,557	177,068
Loans and leases, net of unearned income	184,464	179,568
Commercial - unsecured | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	91	1,598
Commercial - unsecured | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	85	0
Commercial - industrial, financial and agricultural
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	42,497	59,032
≥ 90 Days Past Due and Accruing	884	1,119
Non- accrual	36,242	50,150
Current	4,451,999	4,345,516
Loans and leases, net of unearned income	4,494,496	4,404,548	4,288,823
Commercial - industrial, financial and agricultural | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	3,325	6,825
Commercial - industrial, financial and agricultural | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	2,046	938
Real-estate - home equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	20,215	20,471
≥ 90 Days Past Due and Accruing	4,122	3,061
Non- accrual	6,648	6,708
Current	1,325,900	1,431,666
Loans and leases, net of unearned income	1,346,115	1,452,137	1,469,152
Real-estate - home equity | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	7,063	7,144
Real-estate - home equity | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	2,382	3,558
Real estate - residential mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	44,242	48,089
≥ 90 Days Past Due and Accruing	4,414	4,433
Non- accrual	15,736	14,668
Current	2,526,551	2,202,955
Loans and leases, net of unearned income	2,570,793	2,251,044	2,173,548
Real estate - residential mortgage | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	17,801	20,796
Real estate - residential mortgage | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	6,291	8,192
Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	5,432	9,370
≥ 90 Days Past Due and Accruing	479	0
Non- accrual	3,627	6,881
Current	113,229	108,502
Loans and leases, net of unearned income	118,661	117,872
Construction | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	1,326	2,489
Construction | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	0	0
Construction - commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	411	19
≥ 90 Days Past Due and Accruing	0	0
Non- accrual	19	19
Current	710,302	726,707
Loans and leases, net of unearned income	710,713	726,726
Construction - commercial | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	392	0
Construction - commercial | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	0	0
Construction - other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	1,483	490
≥ 90 Days Past Due and Accruing	0	0
Non- accrual	187	490
Current	82,787	71,511
Loans and leases, net of unearned income	84,270	72,001
Construction - other | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	1,296	0
Construction - other | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	0	0
Real estate - construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	7,326	9,879
≥ 90 Days Past Due and Accruing	479	0
Non- accrual	3,833	7,390
Current	906,318	906,720
Loans and leases, net of unearned income	913,644	916,599	979,857
Real estate - construction | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	3,014	2,489
Real estate - construction | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	0	0
Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	735	404
≥ 90 Days Past Due and Accruing	94	66
Non- accrual	0	0
Current	64,066	55,629
Loans and leases, net of unearned income	64,801	56,033
Consumer | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	521	267
Consumer | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	120	71
Consumer - indirect
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	3,493	3,748
≥ 90 Days Past Due and Accruing	148	343
Non- accrual	0	0
Current	395,919	359,405
Loans and leases, net of unearned income	399,412	363,153
Consumer - indirect | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	2,890	2,908
Consumer - indirect | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	455	497
Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	4,228	4,152
≥ 90 Days Past Due and Accruing	242	409
Non- accrual	0	0
Current	459,985	415,034
Loans and leases, net of unearned income	464,213	419,186	390,708
Consumer | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	3,411	3,175
Consumer | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	575	568
Equipment lease financing, other and overdrafts
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	18,732	20,889
≥ 90 Days Past Due and Accruing	247	319
Non- accrual	17,419	19,268
Current	274,239	267,112
Loans and leases, net of unearned income	292,971	288,001	$ 285,021
Equipment lease financing, other and overdrafts | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	923	1,005
Equipment lease financing, other and overdrafts | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Non-accrual	$ 143	$ 297