RETIREMENT PLANS: (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Compensation and Retirement Disclosure [Abstract]
Service cost - benefits earned	$ 2,238	$ 4,872	$ 3,542
Interest cost on projected benefit obligation	3,383	3,667	3,688
Expected return on plan assets	(3,309)	(3,258)	(4,003)
Net amortization and deferral	2,075	2,434	1,152
Net periodic pension cost	4,387	7,715	4,379
Net loss (gain) during the period	(14,697)	3,842	17,868
Curtailment gain	0	(5,700)	0
Amortization of prior service cost	16	(166)	(166)
Amortization of unrecognized gain (loss)	(2,091)	(2,270)	(986)
Total recognized in other comprehensive income (loss)	(16,772)	(4,294)	16,716
Total recognized net periodic pension cost and other comprehensive income	$ (12,385)	$ 3,421	$ 21,095