Loans and Allowance for Credit Losses Allowance for Loan Losses by Portfolio Segment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	$ 163,841	$ 177,701	$ 169,054	$ 184,144
Loans charged off	(10,746)	(15,372)	(21,901)	(21,136)
Recoveries of loans previously charged off	7,278	2,967	11,556	6,158
Net loans charged off	(3,468)	(12,405)	(10,345)	(14,978)
Provision for loan losses	2,173	2,189	3,837	(1,681)
Ending Balance	162,546	167,485	162,546	167,485
Provision for loan losses gross	338	11	200	180
Provision for credit losses	2,511	2,200	4,041	(1,500)
Real-estate commercial mortage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	48,311	52,860	47,866	53,493
Loans charged off	(1,474)	(1,642)	(2,056)	(2,351)
Recoveries of loans previously charged off	1,367	451	2,192	887
Net loans charged off	(107)	(1,191)	136	(1,464)
Provision for loan losses	(4,464)	(989)	(4,262)	(1,349)
Ending Balance	43,740	50,680	43,740	50,680
Commercial - industrial, financial, and agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	54,333	57,150	57,098	51,378
Loans charged off	(4,625)	(11,166)	(10,813)	(13,029)
Recoveries of loans previously charged off	2,931	1,471	5,250	2,257
Net loans charged off	(1,694)	(9,695)	(5,563)	(10,772)
Provision for loan losses	(884)	1,715	220	8,564
Ending Balance	51,755	49,170	51,755	49,170
Real-estate - home equity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	22,524	23,481	22,405	28,271
Loans charged off	(1,045)	(870)	(2,586)	(1,638)
Recoveries of loans previously charged off	350	189	688	440
Net loans charged off	(695)	(681)	(1,898)	(1,198)
Provision for loan losses	4,341	(294)	5,663	(4,567)
Ending Balance	26,170	22,506	26,170	22,506
Real-estate - residential mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	19,928	23,235	21,375	29,072
Loans charged off	(340)	(783)	(1,408)	(2,064)
Recoveries of loans previously charged off	420	187	556	346
Net loans charged off	80	(596)	(852)	(1,718)
Provision for loan losses	1,218	148	703	(4,567)
Ending Balance	21,226	22,787	21,226	22,787
Real-estate - construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	6,282	8,487	6,529	9,756
Loans charged off	(742)	(87)	(1,068)	(87)
Recoveries of loans previously charged off	1,563	231	1,946	1,378
Net loans charged off	821	144	878	1,291
Provision for loan losses	(1,331)	(882)	(1,635)	(3,298)
Ending Balance	5,772	7,749	5,772	7,749
Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	2,324	2,527	2,585	3,015
Loans charged off	(569)	(357)	(1,576)	(1,137)
Recoveries of loans previously charged off	539	368	735	609
Net loans charged off	(30)	11	(841)	(528)
Provision for loan losses	690	70	1,240	121
Ending Balance	2,984	2,608	2,984	2,608
Leasing and other and overdrafts [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	2,974	1,653	2,468	1,799
Loans charged off	(1,951)	(467)	(2,394)	(830)
Recoveries of loans previously charged off	108	70	189	241
Net loans charged off	(1,843)	(397)	(2,205)	(589)
Provision for loan losses	1,387	359	2,255	405
Ending Balance	2,518	1,615	2,518	1,615
Unallocated [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	7,165	8,308	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	1,216	2,062	(347)	3,010
Ending Balance	$ 8,381	$ 10,370	$ 8,381	$ 10,370