RETIREMENT PLANS: (Details 5) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 70,132	$ 60,602	$ 62,565
Quoted Prices in Active Markets for Identical Assets - Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	58,566	46,338
Significant Other Observable Inputs - Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11,566	14,264
Significant Observable Inputs - Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	51,170	44,052
Equity Securities | Quoted Prices in Active Markets for Identical Assets - Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	51,170	44,052
Equity Securities | Significant Other Observable Inputs - Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Equity Securities | Significant Observable Inputs - Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Debt securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11,566	14,264
Debt securities | Quoted Prices in Active Markets for Identical Assets - Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Debt securities | Significant Other Observable Inputs - Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11,566	14,264
Debt securities | Significant Observable Inputs - Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Investment Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,396	2,286
Investment Funds | Quoted Prices in Active Markets for Identical Assets - Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,396	2,286
Investment Funds | Significant Other Observable Inputs - Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Investment Funds | Significant Observable Inputs - Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0	$ 0