FAIR VALUES OF FINANCIAL INSTRUMENTS: (Details 4) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Carrying amount and estimated fair value of financial instruments
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Credit Losses on Debt Securities Held	$ 2,974	$ 7,132	$ 13,974	$ 13,995
Securities available-for-sale	784,916	814,931
Restricted Stock	10,390	10,379
Accrued interest receivable	13,970	12,913
Deposits	(2,436,727)	(2,458,653)
Level 1
Carrying amount and estimated fair value of financial instruments
Cash and due from banks	23,418	20,682
Securities available-for-sale		0
Level 2
Carrying amount and estimated fair value of financial instruments
Cash and due from banks	50,970	53,425
Federal funds sold		0
Securities available-for-sale	778,523	796,646
Accrued interest receivable	3,005	3,596
Deposits	(2,426,128)	(2,456,900)
Short-term borrowings	(69,656)	(57,686)
Federal Home Loan Bank advances	0	0
Accrued interest payable	(609)	(372)
Level 3
Carrying amount and estimated fair value of financial instruments
Securities available-for-sale	6,393	18,285
Loans, net	1,889,795	1,878,166
Accrued interest receivable	10,965	9,317
Reported Value Measurement [Member]
Carrying amount and estimated fair value of financial instruments
Cash and due from banks	74,388	74,107
Federal funds sold		0
Securities available-for-sale	784,916	814,931
Restricted Stock	10,390	10,379
Loans, net	1,933,552	1,886,852
Accrued interest receivable	13,970	12,913
Deposits	(2,436,727)	(2,458,653)
Short-term borrowings	(69,656)	(57,686)
Federal Home Loan Bank advances	0	0
Accrued interest payable	(609)	(372)
Estimate of Fair Value Measurement [Member]
Carrying amount and estimated fair value of financial instruments
Cash and due from banks	74,388	74,107
Federal funds sold		0
Securities available-for-sale	784,916	814,931
Loans, net	1,889,795	1,878,166
Accrued interest receivable	13,970	12,913
Deposits	(2,426,128)	(2,456,900)
Short-term borrowings	(69,656)	(57,686)
Federal Home Loan Bank advances	0	0
Accrued interest payable	$ (609)	$ (372)

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Fair value portion of federal funds sold and securities borrowed or purchased under agreements to resell.

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Fair value portion of borrowing from Federal Home Loan Bank (FHLBank).

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Amount of interest payable on debt, including, but not limited to, trade payables.

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Carrying amount as of the balance sheet date of interest earned but not received. Also called accrued interest or accrued interest receivable.

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The cumulative amount of credit losses recognized in earnings related to debt securities held for which a portion of an other than temporary impairment (OTTI) was recognized in other comprehensive income (a component of shareholders' equity).

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Investments which are not defined as or included in marketable (debt, equity, or other) securities whose use is restricted in whole or in part, generally by contractual agreements or regulatory requirements. For use in an unclassified balance sheet.

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