RETIREMENT PLANS: (Details 1) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Retirement Benefits [Abstract]
Defined Benefit Plan, Benefit Obligation, Benefits Paid	$ 3,921	$ 4,264
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)
Benefits paid	(3,921)	(4,264)
Benefit obligation at December 31	102,791	87,796	98,096
Reconciliation of fair value of plan assets:
Fair value of plan assets at January 1	64,335	71,449
Actual return on plan assets	11,456	(5,464)
Employer contributions	2,092	2,614
Fair value of plan assets at December 31	73,962	64,335	$ 71,449
Funded status at December 31 (plan assets less benefit obligation)	$ (28,829)	$ (23,461)