Acquisitions and FDIC Indemnification Asset (Details Textual) - USD ($)	3 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Gain on Sale of certain assets and liabilities of Insurance Brokerage Operation	$ (199,000)	$ 0	$ 12,822,000
Assets		2,982,342,000		$ 2,988,527,000
Goodwill		34,355,000		34,355,000
Loans and Leases Receivable, Net of Loans with Deteriorated Credit Quality, Covered		4,400,000		5,100,000
First National Bank Of Danville [Member]
Business Acquisition [Line Items]
Reimbursements from the FDIC		19,400,000
Business Aquisition, Loss Sharing Agreement Losses On Assets Threshold		$ 29,000,000
Business Acquisition Loss Sharing Agreement Losses In Excess Of Threshold To Be Reimbursed Percentage		95.00%
Business Acquisition, Loss Sharing Agreement Losses Up To Threshold To Be Reimbursed Percentage		80.00%
Forrest Sherer Insurance [Domain]
Business Acquisition [Line Items]
Assets				13,000,000	$ 15,800,000
Insurance Services Revenue				7,600,000	8,300,000
Operating Income (Loss)				$ 168,000	$ 554,000