RETIREMENT PLANS: (Details 9) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Change in benefit obligation:
Benefit obligation at January 1	$ 98,135	$ 81,469
Service cost	2,153	2,040	$ 2,238
Interest cost	3,516	3,756	3,383
Actuarial (gain) loss	(8,802)	22,274
Benefits paid	(4,147)	(4,256)
Benefit obligation at December 31	90,855	98,135	81,469
Funded status at December 31	(30,253)	(35,570)
Supplemental Employee Retirement Plans, Defined Benefit
Change in benefit obligation:
Benefit obligation at January 1	4,559	4,088
Service cost	63	53
Interest cost	173	175
Plan participants' contributions	57	39
Actuarial (gain) loss	(200)	456
Benefits paid	(269)	(252)
Benefit obligation at December 31	4,383	4,559	$ 4,088
Funded status at December 31	$ 4,383	$ 4,559