RETIREMENT PLANS: (Details 9) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Change in benefit obligation:
Benefit obligation at January 1	$ 90,855	$ 98,135
Service cost	1,882	2,153	$ 2,040
Interest cost	3,729	3,516	3,756
Actuarial (gain) loss	2,839	(8,802)
Benefits paid	(6,072)	(4,147)
Benefit obligation at December 31	93,233	90,855	98,135
Funded status at December 31	(23,101)	(30,253)
Supplemental Employee Retirement Plans, Defined Benefit
Change in benefit obligation:
Benefit obligation at January 1	4,383	4,559
Service cost	55	63
Interest cost	186	173
Plan participants' contributions	69	57
Actuarial (gain) loss	(144)	(200)
Benefits paid	(273)	(269)
Benefit obligation at December 31	4,276	4,383	$ 4,559
Funded status at December 31	$ 4,276	$ 4,383