RETIREMENT AND DEFERRED COMPENSATION PLANS - Allocations for Plan Asset Holding and Target Allocation for Company's Plan Asset (Details)	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	100.00%
Percentage of Plan Assets at Year-End	100.00%	100.00%
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	19.00%
Percentage of Plan Assets at Year-End	19.00%	23.00%
Overseas quoted equities
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	19.00%
Percentage of Plan Assets at Year-End	19.00%	23.00%
Debt securities
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	81.00%
Percentage of Plan Assets at Year-End	80.00%	77.00%
U.K. government bonds
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	65.00%
Percentage of Plan Assets at Year-End	64.00%	62.00%
U.K. corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	16.00%
Percentage of Plan Assets at Year-End	16.00%	15.00%
Cash
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	0.00%
Percentage of Plan Assets at Year-End	1.00%	0.00%

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- Definition

Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 55
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4179-114921

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(i)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

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Percentage of actual investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(i)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

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