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EMPLOYEE BENEFIT PLANS (Additional Information) (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]      
Required service period for employee participation 30 days    
Basic contributions as a percentage of annual salary 50.00%    
Company matching contribution, percent of match 200.00%    
Company matching contribution, percent of employees' annual pay 3.00%    
Contribution to the qualified defined contribution plans $ 23,321 $ 19,746 $ 12,753
Maximum age to receive health care coverage 65 years    
Defined Benefit Plan, Accumulated Benefit Obligation $ 148,011 $ 108,838  
Pension Benefits [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plans, Estimated Future Employer Contributions in Next Fiscal Year $ 34,800    
Pension Benefits [Member] | Equity Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Plan asset allocations 54.00%    
Pension Benefits [Member] | Fixed Income Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Plan asset allocations 40.00%    
Pension Benefits [Member] | Real Estate [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Plan asset allocations 6.00%