ACQUISITIONS AND FDIC INDEMNIFICATION ASSET: (Details Textual) - USD ($)	3 Months Ended								9 Months Ended	12 Months Ended			54 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2013	Aug. 16, 2013
Business Acquisition [Line Items]
Gain on Sale of certain assets and liabilities of Insurance Brokerage Operation		$ (199,000)							$ 12,800,000	$ 0	$ 12,822,000	$ 0
Deposits	$ 2,458,653,000				$ 2,428,526,000					2,458,653,000	2,428,526,000
Goodwill	34,355,000				34,355,000					34,355,000	34,355,000
Reimbursements from the FDIC													$ (24,300,000)
Covered loans	4,300,000				5,100,000					4,300,000	5,100,000
Assets	3,000,668,000				2,988,527,000					3,000,668,000	2,988,527,000
Net Income (Loss) Attributable to Parent	$ 2,616,000	$ 8,794,000	$ 8,352,000	$ 9,369,000	8,344,000	$ 8,162,000	$ 8,232,000	$ 13,675,000		29,131,000	38,413,000	30,196,000
Bank of America
Business Acquisition [Line Items]
Goodwill recorded, which is expected to be tax deductable														$ 1,900
First National Bank Of Danville
Business Acquisition [Line Items]
Losses on assets, threshold under loss-sharing agreement (up to $29 million)										$ 29,000,000
Percentage of losses to be reimbursed by the FDIC, on losses up to the threshold amount (percent)										80.00%
Percentage of losses to be reimbursed by the FDIC, on losses exceeding the threshold amount (percent)										95.00%
Forrest Sherer Insurance [Domain]
Business Acquisition [Line Items]
Revenues											7,600,000	8,300,000
Operating Income (Loss)											168,000	544,000
Goodwill				$ 5,100,000
Assets					$ 13,000,000						$ 13,000,000	$ 15,800,000