Loans and Leases and Allowance for Credit Losses - Balance and activity in allowance for credit losses by portfolio segment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	$ 61,226	$ 63,424	$ 70,990
Charge-Offs	(13,158)	(12,202)	(12,361)
Recoveries	7,045	6,204	5,595
Provision	9,500	3,800	(800)
Ending Balance	64,613	61,226	63,424
Loans Receivable
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	58,914	61,422	68,448
Charge-Offs	(13,158)	(12,202)	(12,361)
Recoveries	7,045	6,204	5,595
Provision	8,402	3,490	(260)
Ending Balance	61,203	58,914	61,422
Loans Receivable | Home equity lines of credit
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	5,177	4,599	5,956
Charge-Offs	(1,194)	(1,435)	(1,690)
Recoveries	423	567	386
Provision	346	1,446	(53)
Ending Balance	4,752	5,177	4,599
Loans Receivable | Indirect auto
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	1,550	1,802	1,393
Charge-Offs	(1,277)	(1,420)	(1,399)
Recoveries	228	284	233
Provision	498	884	1,575
Ending Balance	999	1,550	1,802
Loans Receivable | Commercial | Owner occupied commercial real estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	14,776	16,446	18,016
Charge-Offs	(303)	(406)	(2,029)
Recoveries	1,227	980	706
Provision	(3,493)	(2,244)	(247)
Ending Balance	12,207	14,776	16,446
Loans Receivable | Commercial | Income producing commercial real estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	9,381	8,843	11,548
Charge-Offs	(3,304)	(2,985)	(1,433)
Recoveries	1,064	178	580
Provision	3,932	3,345	(1,852)
Ending Balance	11,073	9,381	8,843
Loans Receivable | Commercial | Construction
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	10,523	13,405	9,553
Charge-Offs	(622)	(1,023)	(837)
Recoveries	734	1,018	821
Provision	(298)	(2,877)	3,868
Ending Balance	10,337	10,523	13,405
Loans Receivable | Commercial | Equipment financing
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	0	0	0
Charge-Offs	(1,536)	0	0
Recoveries	460	0	0
Provision	6,528	0	0
Ending Balance	5,452	0	0
Loans Receivable | Commercial | Commercial & industrial
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	3,971	3,810	4,433
Charge-Offs	(1,669)	(1,528)	(1,830)
Recoveries	1,390	1,768	1,689
Provision	1,110	(79)	(482)
Ending Balance	4,802	3,971	3,810
Loans Receivable | Residential | Construction
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	2,729	3,264	4,002
Charge-Offs	(54)	(129)	(533)
Recoveries	376	178	79
Provision	(618)	(584)	(284)
Ending Balance	2,433	2,729	3,264
Loans Receivable | Residential | Residential mortgage
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	10,097	8,545	12,719
Charge-Offs	(754)	(1,473)	(1,151)
Recoveries	336	314	301
Provision	(1,384)	2,711	(3,324)
Ending Balance	8,295	10,097	8,545
Loans Receivable | Consumer direct
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	710	708	828
Charge-Offs	(2,445)	(1,803)	(1,459)
Recoveries	807	917	800
Provision	1,781	888	539
Ending Balance	853	710	708
Loans Receivable | Allowance for unfunded commitments
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	2,312	2,002	2,542
Charge-Offs	0	0	0
Recoveries	0	0	0
Provision	1,098	310	(540)
Ending Balance	$ 3,410	$ 2,312	$ 2,002