RETIREMENT PLANS: (Details 5) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 73,962	$ 64,335	$ 71,449
Quoted Prices in Active Markets for Identical Assets - Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	60,858	53,683
Significant Other Observable Inputs - Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13,104	10,652
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	51,334	43,931
Equity Securities | Quoted Prices in Active Markets for Identical Assets - Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	51,334	43,931
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	13,104	10,652
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	13,104	10,652
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	9,524	9,752
Investment Funds | Quoted Prices in Active Markets for Identical Assets - Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	9,524	9,752
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