Loans and Allowance for Credit Losses Allowance for Loan Losses by Portfolio Segment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	$ 169,054	$ 184,144
Loans charged off	(11,155)	(5,764)
Recoveries of loans previously charged off	4,278	3,191
Net loans charged off	(6,877)	(2,573)
Provision for loan losses	1,664	(3,870)
Ending Balance	163,841	177,701
Provision for loan losses gross	(134)	170
Provision for Loan and Lease Losses	1,530	(3,700)
Real-estate commercial mortage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	47,866	53,493
Loans charged off	(582)	(709)
Recoveries of loans previously charged off	825	436
Net loans charged off	243	(273)
Provision for loan losses	202	(360)
Ending Balance	48,311	52,860
Commercial - industrial, financial, and agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	57,098	51,378
Loans charged off	(6,188)	(1,863)
Recoveries of loans previously charged off	2,319	786
Net loans charged off	(3,869)	(1,077)
Provision for loan losses	1,104	6,849
Ending Balance	54,333	57,150
Real-estate - home equity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	22,405	28,271
Loans charged off	(1,541)	(768)
Recoveries of loans previously charged off	338	251
Net loans charged off	(1,203)	(517)
Provision for loan losses	1,322	(4,273)
Ending Balance	22,524	23,481
Real-estate - residential mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	21,375	29,072
Loans charged off	(1,068)	(1,281)
Recoveries of loans previously charged off	136	159
Net loans charged off	(932)	(1,122)
Provision for loan losses	(515)	(4,715)
Ending Balance	19,928	23,235
Real-estate - construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	6,529	9,756
Loans charged off	(326)	0
Recoveries of loans previously charged off	383	1,147
Net loans charged off	57	1,147
Provision for loan losses	(304)	(2,416)
Ending Balance	6,282	8,487
Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	2,585	3,015
Loans charged off	(1,007)	(780)
Recoveries of loans previously charged off	196	241
Net loans charged off	(811)	(539)
Provision for loan losses	550	51
Ending Balance	2,324	2,527
Leasing and other and overdrafts [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	2,468	1,799
Loans charged off	(443)	(363)
Recoveries of loans previously charged off	81	171
Net loans charged off	(362)	(192)
Provision for loan losses	868	46
Ending Balance	2,974	1,653
Unallocated [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	8,728	7,360
Loans charged off	0	0
Recoveries of loans previously charged off	0	0
Net loans charged off	0	0
Provision for loan losses	(1,563)	948
Ending Balance	$ 7,165	$ 8,308