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EMPLOYEE BENEFIT PLANS - Weighted average asset allocation by asset category along with target allocation (Details) - Retirement Income Plan | 12 Months Ended |
--- | --- | ---
Dec. 31, 2015 | Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items] |  |
Percentage of plan assets | 100.00% | 100.00%
Target Allocation for 2016 | 100.00% |
Cash and Cash Equivalents |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Percentage of plan assets | 0.70% | 1.00%
Target Allocation for 2016, Minimum | 0.00% |
Target Allocation for 2016, Maximum | 5.00% |
Debt Securities - Core Fixed Income |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Percentage of plan assets | 25.80% | 24.30%
Target Allocation for 2016, Minimum | 15.00% |
Target Allocation for 2016, Maximum | 50.00% |
Domestic Equity Securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Percentage of plan assets | 38.50% | 37.00%
Target Allocation for 2016, Minimum | 0.00% |
Target Allocation for 2016, Maximum | 40.00% |
International Equity Securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Percentage of plan assets | 23.20% | 22.80%
Target Allocation for 2016, Minimum | 0.00% |
Target Allocation for 2016, Maximum | 30.00% |
Real Estate |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Percentage of plan assets | 7.20% | 10.50%
Target Allocation for 2016, Minimum | 0.00% |
Target Allocation for 2016, Maximum | 20.00% |
Real Return |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Percentage of plan assets | 0.00% | 1.60%
Target Allocation for 2016, Minimum | 0.00% |
Target Allocation for 2016, Maximum | 20.00% |
Alternative/Opportunistic/Special |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Percentage of plan assets | 4.60% | 2.80%
Target Allocation for 2016, Minimum | 0.00% |
Target Allocation for 2016, Maximum | 20.00% |

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