OTHER COMPREHENSIVE INCOME (LOSS): (Details 1) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance, January 1	$ (14,164)	$ (9,401)
Current Period Change	(540)	(4,763)
Ending balance, December 31	(14,704)	(14,164)
Unrealized Gains and Losses on Available-for-Sale Securities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance, January 1	(1,077)	9,053
Current Period Change	3,335	(10,130)
Ending balance, December 31	2,258	(1,077)
Unrealized gains losses on securities available-for-sale without other than temporary impairment
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance, January 1	(3,018)	5,855
Current Period Change	1,647	(8,873)
Ending balance, December 31	(1,371)	(3,018)
Unrealized gains losses on securities available-for-sale with other than temporary impairment
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance, January 1	1,941	3,198
Current Period Change	1,688	(1,257)
Ending balance, December 31	3,629	1,941
Retirement Plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance, January 1	(13,087)	(18,454)
Current Period Change	(3,875)	(5,367)
Ending balance, December 31	$ (16,962)	$ (13,087)