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RETIREMENT AND DEFERRED COMPENSATION PLANS - Allocations for Plan Asset Holding and Target Allocation for Company's Plan Asset (Detail)
Dec. 31, 2017
Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]    
Target Allocation 100.00%  
Percentage of Plan Assets at Year-End 100.00% 100.00%
Cash    
Defined Benefit Plan Disclosure [Line Items]    
Target Allocation 0.00%  
Percentage of Plan Assets at Year-End 2.00% 1.00%
Equity securities    
Defined Benefit Plan Disclosure [Line Items]    
Target Allocation 26.00%  
Percentage of Plan Assets at Year-End 26.00% 40.00%
Equity securities | U.K. quoted equities    
Defined Benefit Plan Disclosure [Line Items]    
Target Allocation 0.00%  
Percentage of Plan Assets at Year-End 0.00% 14.00%
Equity securities | Overseas quoted equities    
Defined Benefit Plan Disclosure [Line Items]    
Target Allocation 26.00%  
Percentage of Plan Assets at Year-End 26.00% 26.00%
Debt securities    
Defined Benefit Plan Disclosure [Line Items]    
Target Allocation 74.00%  
Percentage of Plan Assets at Year-End 72.00% 59.00%
Debt securities | U.K. Government bonds    
Defined Benefit Plan Disclosure [Line Items]    
Target Allocation 59.00%  
Percentage of Plan Assets at Year-End 58.00% 47.00%
Debt securities | U.K. corporate bonds    
Defined Benefit Plan Disclosure [Line Items]    
Target Allocation 15.00%  
Percentage of Plan Assets at Year-End 14.00% 12.00%