Loans and Allowance for Credit Losses Allowance for Loan Losses by Portfolio Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	$ 162,546	$ 167,485	$ 169,054	$ 184,144
Loans charged off	(7,672)	(5,561)	(29,573)	(26,697)
Recoveries of loans previously charged off	3,592	4,503	15,148	10,661
Net loans charged off	(4,080)	(1,058)	(14,425)	(16,036)
Provision for loan losses	4,060	709	7,897	(972)
Ending Balance	162,526	167,136	162,526	167,136
Provision for loan losses gross	81	291	285	470
Provision for credit losses	4,141	1,000	8,182	(500)
Real-estate commercial mortage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	43,740	50,680	47,866	53,493
Loans charged off	(1,350)	(660)	(3,406)	(3,011)
Recoveries of loans previously charged off	296	842	2,488	1,729
Net loans charged off	(1,054)	182	(918)	(1,282)
Provision for loan losses	3,171	825	(1,091)	(524)
Ending Balance	45,857	51,687	45,857	51,687
Commercial - industrial, financial, and agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	51,755	49,170	57,098	51,378
Loans charged off	(3,144)	(1,640)	(13,957)	(14,669)
Recoveries of loans previously charged off	1,539	1,598	6,789	3,855
Net loans charged off	(1,605)	(42)	(7,168)	(10,814)
Provision for loan losses	(1,871)	(405)	(1,651)	8,159
Ending Balance	48,279	48,723	48,279	48,723
Real-estate - home equity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	26,170	22,506	22,405	28,271
Loans charged off	(709)	(940)	(3,295)	(2,578)
Recoveries of loans previously charged off	241	304	929	744
Net loans charged off	(468)	(636)	(2,366)	(1,834)
Provision for loan losses	1,419	180	7,082	(4,387)
Ending Balance	27,121	22,050	27,121	22,050
Real-estate - residential mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	21,226	22,787	21,375	29,072
Loans charged off	(802)	(1,035)	(2,210)	(3,099)
Recoveries of loans previously charged off	228	201	784	547
Net loans charged off	(574)	(834)	(1,426)	(2,552)
Provision for loan losses	1,452	(609)	2,155	(5,176)
Ending Balance	22,104	21,344	22,104	21,344
Real-estate - construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	5,772	7,749	6,529	9,756
Loans charged off	(150)	(114)	(1,218)	(201)
Recoveries of loans previously charged off	898	898	2,844	2,276
Net loans charged off	748	784	1,626	2,075
Provision for loan losses	23	(964)	(1,612)	(4,262)
Ending Balance	6,543	7,569	6,543	7,569
Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	2,984	2,608	2,585	3,015
Loans charged off	(685)	(650)	(2,261)	(1,787)
Recoveries of loans previously charged off	222	314	957	923
Net loans charged off	(463)	(336)	(1,304)	(864)
Provision for loan losses	852	282	2,092	403
Ending Balance	3,373	2,554	3,373	2,554
Leasing and other and overdrafts [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	2,518	1,615	2,468	1,799
Loans charged off	(832)	(522)	(3,226)	(1,352)
Recoveries of loans previously charged off	168	346	357	587
Net loans charged off	(664)	(176)	(2,869)	(765)
Provision for loan losses	1,075	223	3,330	628
Ending Balance	2,929	1,662	2,929	1,662
Unallocated [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	8,381	10,370	8,728	7,360
Loans charged off	0	0	0	0
Recoveries of loans previously charged off	0	0	0	0
Net loans charged off	0	0	0	0
Provision for loan losses	(2,061)	1,177	(2,408)	4,187
Ending Balance	$ 6,320	$ 11,547	$ 6,320	$ 11,547