RETIREMENT PLANS: (Details 1) - 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
Reconciliation of fair value of plan assets:
Fair value of plan assets at January 1	60,602	62,565
Actual return on plan assets	12,418	(205)
Employer contributions	3,184	2,389
Benefits paid	(6,072)	(4,147)
Fair value of plan assets at December 31	70,132	60,602	$ 62,565
Funded status at December 31 (plan assets less benefit obligation)	$ (23,101)	$ (30,253)