RETIREMENT PLANS: (Details 7) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net loss (gain) during the period	$ 23,111	$ (14,697)	$ 3,842
Amortization of prior service cost	9	16	(166)
Amortization of unrecognized gain (loss)	(759)	(2,091)	(2,270)
Total recognized in other comprehensive income (loss)	12,537	(16,772)	(4,294)
Supplemental Employee Retirement Plans, Defined Benefit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net loss (gain) during the period	932	(333)	442
Amortization of prior service cost	0	0	0
Amortization of unrecognized gain (loss)	(7)	(68)	(79)
Total recognized in other comprehensive income (loss)	$ 925	$ (401)	$ 363