Loans and Allowance for Credit Losses Past Due Loan Status and Non-Accrual Loans by Portfolio Segment (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 186,153	$ 196,268
≥ 90 Days Past Due and Accruing	12,628	10,010
Non- accrual	111,116	124,749
Current	15,606,816	15,571,979
Loans, net of unearned income	15,792,969	15,768,247	$ 15,346,617
Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	50,905	40,709
Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	11,504	20,800
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	123,744	134,759
Real-estate - commercial mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	48,776	49,126
≥ 90 Days Past Due and Accruing	3,970	625
Non- accrual	35,308	34,822
Current	6,255,699	6,315,678
Loans, net of unearned income	6,304,475	6,364,804	6,262,008
Real-estate - commercial mortgage \| Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	8,537	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	961	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	39,278	35,447
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	60,240	63,647
≥ 90 Days Past Due and Accruing	299	1,360
Non- accrual	43,005	52,255
Current	4,048,347	4,068,793
Loans, net of unearned income	4,108,587	4,132,440
Commercial \| Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	14,687	4,778
Commercial \| Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,249	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	43,304	53,615
Commercial - unsecured
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,253	1,009
≥ 90 Days Past Due and Accruing	129	45
Non- accrual	612	649
Current	154,762	166,848
Loans, net of unearned income	156,015	167,857
Commercial - unsecured \| Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	350	305
Commercial - unsecured \| Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	162	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	741	694
Commercial - industrial, financial and agricultural
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	61,493	64,656
≥ 90 Days Past Due and Accruing	428	1,405
Non- accrual	43,617	52,904
Current	4,203,109	4,235,641
Loans, net of unearned income	4,264,602	4,300,297	4,245,849
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	15,037	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	2,411	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	44,045	54,309
Real-estate - home equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	21,389	24,162
≥ 90 Days Past Due and Accruing	2,885	2,372
Non- accrual	8,801	9,135
Current	1,470,006	1,535,557
Loans, net of unearned income	1,491,395	1,559,719	1,579,739
Real-estate - home equity \| Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	8,053	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	1,650	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	11,686	11,507
Real estate - residential mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	39,720	39,823
≥ 90 Days Past Due and Accruing	4,619	5,280
Non- accrual	14,269	15,691
Current	2,054,810	1,914,888
Loans, net of unearned income	2,094,530	1,954,711	1,784,712
Real estate - residential mortgage \| Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	15,333	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	5,499	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	18,888	20,971
Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	9,554	12,206
≥ 90 Days Past Due and Accruing	0	0
Non- accrual	8,810	11,767
Current	133,511	150,896
Loans, net of unearned income	143,065	163,102
Construction \| Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	560	0
Construction \| Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	184	439
Construction \| Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	8,810	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	768,628	765,314
Loans, net of unearned income	768,647	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	78,503	77,403
Loans, net of unearned income	78,993	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	10,063	13,322
≥ 90 Days Past Due and Accruing	198	0
Non- accrual	9,121	12,197
Current	980,642	993,613
Loans, net of unearned income	990,705	1,006,935	938,900
Real-estate - construction \| Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	560	686
Real-estate - construction \| Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	184	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	9,319	12,197
Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	191	385
≥ 90 Days Past Due and Accruing	83	70
Non- accrual	0	0
Current	62,142	54,828
Loans, net of unearned income	62,333	55,213
Consumer \| Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	45	260
Consumer \| Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	63	55
Consumer \| Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	83	70
Consumer - indirect
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	3,296	3,907
≥ 90 Days Past Due and Accruing	269	226
Non- accrual	0	0
Current	294,686	254,663
Loans, net of unearned income	297,982	258,570
Consumer - indirect \| Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,535	3,055
Consumer - indirect \| Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	492	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	269	226
Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	3,487	4,292
≥ 90 Days Past Due and Accruing	352	296
Non- accrual	0	0
Current	356,828	309,491
Loans, net of unearned income	360,315	313,783	283,156
Consumer \| Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,580	3,315
Consumer \| Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	555	681
Consumer \| Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	352	296
Leasing, other and overdrafts
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,225	887
≥ 90 Days Past Due and Accruing	176	32
Non- accrual	0	0
Current	285,722	267,111
Loans, net of unearned income	286,947	267,998	$ 252,253
Leasing, other and overdrafts \| Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	805	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	244	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	$ 176	$ 32

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

Jun. 30, 2018

Dec. 31, 2017

Jun. 30, 2017

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

Total Past Due

$ 186,153

$ 196,268

≥ 90 Days Past Due and Accruing

12,628

10,010

Non- accrual