RETIREMENT PLANS: (Details 9) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Change in benefit obligation:
Benefit obligation at January 1	$ 87,796	$ 98,096
Service cost	1,218	1,388	$ 1,432
Interest cost	3,465	3,194	3,621
Actuarial (gain) loss	14,233	(10,618)
Defined Benefit Plan, Benefit Obligation, Benefits Paid	3,921	4,264
Benefit obligation at December 31	102,791	87,796	98,096
Funded status at December 31	(28,829)	(23,461)
Supplemental Employee Retirement Plans, Defined Benefit
Change in benefit obligation:
Benefit obligation at January 1	3,420	4,361
Service cost	34	42
Interest cost	145	131
Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant	65	83
Actuarial (gain) loss	626	(872)
Defined Benefit Plan, Benefit Obligation, Benefits Paid	315	325
Benefit obligation at December 31	3,975	3,420	$ 4,361
Funded status at December 31	$ 3,975	$ 3,420