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EMPLOYEE BENEFIT PLANS - Plan assets using fair value hierarchy (Details) (Retirement Income Plan, USD $)
In Thousands, unless otherwise specified
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets $ 6,014us-gaap_DefinedBenefitPlanFairValueOfPlanAssets $ 5,887us-gaap_DefinedBenefitPlanFairValueOfPlanAssets $ 5,282us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
Total
      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 6,014us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
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Level 1
      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 1,447us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
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Level 2
      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 3,766us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
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Level 3
      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 801us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
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Cash and Cash Equivalents | Total
      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 61us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
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Cash and Cash Equivalents | Level 1
      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 61us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
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Cash and Cash Equivalents | Level 2
      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets    [1]    [1]  
Cash and Cash Equivalents | Level 3
      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets    [1]    [1]  
Fixed Income Securities | Total
      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 1,459us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
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Fixed Income Securities | Level 1
      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 589us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
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Fixed Income Securities | Level 2
      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 870us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
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Fixed Income Securities | Level 3
      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets    [2]    [2]  
Domestic Equity Securities | Total
      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 2,226us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
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Domestic Equity Securities | Level 1
      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 797us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
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Domestic Equity Securities | Level 2
      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 1,429us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
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Domestic Equity Securities | Level 3
      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets    [3]    [3]  
International Equity Securities | Total
      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 1,372us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
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International Equity Securities | Level 1
      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets    [4]    [4]  
International Equity Securities | Level 2
      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 1,372us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
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International Equity Securities | Level 3
      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets    [4]    [4]  
Real Estate | Total
      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 631us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
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Real Estate | Level 1
      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets    [5]    [5]  
Real Estate | Level 2
      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets    [5]    [5]  
Real Estate | Level 3
      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 631us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
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Real Return | Total
      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 95us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
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Real Return | Level 1
      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets    [6]    [6]  
Real Return | Level 2
      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 95us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
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Real Return | Level 3
      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets    [6]    [6]  
Alternative/Opportunistic/Special | Total
      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 170us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
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Alternative/Opportunistic/Special | Level 1
      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets    [7]    [7]  
Alternative/Opportunistic/Special | Level 2
      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets    [7]    [7]  
Alternative/Opportunistic/Special | Level 3
      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets $ 170us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
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[1] Cash and cash equivalents, which are used to pay benefits and plan administrative expenses, are held in Rule 2a-7 money market funds.
[2] Fixed income securities are primarily valued using a market approach with inputs that include broker quotes, benchmark yields, base spreads and reported trades.
[3] Domestic equity securities are valued using a market approach based on the quoted market prices of identical instruments in their respective markets.
[4] International equity securities are valued using a market approach based on the quoted market prices of similar instruments in their respective markets.
[5] Real estate fund values are primarily reported by the fund manager and are based on valuation of the underlying investments, which include inputs such as cost, discounted future cash flows, independent appraisals and market based comparable data.
[6] Real return funds invest in global equities, commodities and inflation protected core bonds that are valued primarily using a market approach based on the quoted market prices of identical instruments in their respective markets.
[7] Alternative/Opportunistic/Special funds can invest across the capital structure in both liquid and illiquid securities that are valued using a market approach based on the quoted market prices of identical instruments, or if no market price is available, instruments will be held at their fair market value (which may be cost) as reasonably determined by the investment manager, independent dealers, or pricing services.