Loans and Allowance for Credit Losses Past Due Loan Status and Non-Accrual Loans by Portfolio Segment (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 186,334	$ 196,268
≥ 90 Days Past Due and Accruing	11,676	10,010
Non- accrual	122,966	124,749
Current	15,509,950	15,571,979
Loans, net of unearned income	15,696,284	15,768,247	$ 14,963,177
Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	38,720	40,709
Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	12,972	20,800
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	134,642	134,759
Real-estate - commercial mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	48,881	49,126
≥ 90 Days Past Due and Accruing	1,001	625
Non- accrual	35,183	34,822
Current	6,283,627	6,315,678
Loans, net of unearned income	6,332,508	6,364,804	6,118,533
Real-estate - commercial mortgage \| Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	11,606	9,456
Real-estate - commercial mortgage \| Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,091	4,223
Real-estate - commercial mortgage \| Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	36,184	35,447
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	61,926	63,647
≥ 90 Days Past Due and Accruing	1,935	1,360
Non- accrual	52,336	52,255
Current	4,092,287	4,068,793
Loans, net of unearned income	4,154,213	4,132,440
Commercial \| Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	4,048	4,778
Commercial \| Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	3,607	5,254
Commercial \| Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	54,271	53,615
Commercial - unsecured
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,617	1,009
≥ 90 Days Past Due and Accruing	10	45
Non- accrual	634	649
Current	143,242	166,848
Loans, net of unearned income	144,859	167,857
Commercial - unsecured \| Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	814	305
Commercial - unsecured \| Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	159	10
Commercial - unsecured \| Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	644	694
Commercial - industrial, financial and agricultural
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	63,543	64,656
≥ 90 Days Past Due and Accruing	1,945	1,405
Non- accrual	52,970	52,904
Current	4,235,529	4,235,641
Loans, net of unearned income	4,299,072	4,300,297	4,167,809
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	4,862	5,083
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	3,766	5,264
Commercial - industrial, financial and agricultural \| Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	54,915	54,309
Real-estate - home equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	20,756	24,162
≥ 90 Days Past Due and Accruing	3,280	2,372
Non- accrual	8,745	9,135
Current	1,493,485	1,535,557
Loans, net of unearned income	1,514,241	1,559,719	1,595,901
Real-estate - home equity \| Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	6,401	9,640
Real-estate - home equity \| Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,330	3,015
Real-estate - home equity \| Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	12,025	11,507
Real estate - residential mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	37,707	39,823
≥ 90 Days Past Due and Accruing	4,833	5,280
Non- accrual	15,335	15,691
Current	1,938,817	1,914,888
Loans, net of unearned income	1,976,524	1,954,711	1,665,142
Real estate - residential mortgage \| Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	12,725	11,961
Real estate - residential mortgage \| Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	4,814	6,891
Real estate - residential mortgage \| Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	20,168	20,971
Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	10,422	12,206
≥ 90 Days Past Due and Accruing	0	0
Non- accrual	10,422	11,767
Current	148,060	150,896
Loans, net of unearned income	158,482	163,102
Construction \| Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Construction \| Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	439
Construction \| Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	10,422	11,767
Construction - commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	19	502
≥ 90 Days Past Due and Accruing	0	0
Non- accrual	19	19
Current	748,777	765,314
Loans, net of unearned income	748,796	765,816
Construction - commercial \| Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	483
Construction - commercial \| Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Construction - commercial \| Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	19	19
Construction - other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	490	614
≥ 90 Days Past Due and Accruing	198	0
Non- accrual	292	411
Current	68,363	77,403
Loans, net of unearned income	68,853	78,017
Construction - other \| Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	203
Construction - other \| Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Construction - other \| Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	490	411
Real-estate - construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	10,931	13,322
≥ 90 Days Past Due and Accruing	198	0
Non- accrual	10,733	12,197
Current	965,200	993,613
Loans, net of unearned income	976,131	1,006,935	882,983
Real-estate - construction \| Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	686
Real-estate - construction \| Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	439
Real-estate - construction \| Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	10,931	12,197
Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	377	385
≥ 90 Days Past Due and Accruing	54	70
Non- accrual	0	0
Current	55,681	54,828
Loans, net of unearned income	56,058	55,213
Consumer \| Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	211	260
Consumer \| Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	112	55
Consumer \| Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	54	70
Consumer - indirect
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	3,124	3,907
≥ 90 Days Past Due and Accruing	193	226
Non- accrual	0	0
Current	267,584	254,663
Loans, net of unearned income	270,708	258,570
Consumer - indirect \| Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,253	3,055
Consumer - indirect \| Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	678	626
Consumer - indirect \| Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	193	226
Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	3,501	4,292
≥ 90 Days Past Due and Accruing	247	296
Non- accrual	0	0
Current	323,265	309,491
Loans, net of unearned income	326,766	313,783	288,826
Consumer \| Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,464	3,315
Consumer \| Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	790	681
Consumer \| Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	247	296
Leasing, other and overdrafts
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,015	887
≥ 90 Days Past Due and Accruing	172	32
Non- accrual	0	0
Current	270,027	267,111
Loans, net of unearned income	271,042	267,998	$ 243,983
Leasing, other and overdrafts \| Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	662	568
Leasing, other and overdrafts \| Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	181	287
Leasing, other and overdrafts \| Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 172	$ 32

Loans and Allowance for Credit Losses Past Due Loan Status and Non-Accrual Loans by Portfolio Segment (Details) - USD ($)
$ in Thousands

Mar. 31, 2018

Dec. 31, 2017

Mar. 31, 2017

Financing Receivable, Recorded Investment, Past Due [Line Items]

Total Past Due

$ 186,334

$ 196,268

≥ 90 Days Past Due and Accruing

11,676

10,010

Non- accrual