RETIREMENT AND DEFERRED COMPENSATION PLANS - Fair Values of Plan Assets for Each Major Asset Category Based on Nature and Significant Concentration of Risks in Plan Assets (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 262	$ 228
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	49	52
Overseas quoted equities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	49	52
Debt securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	211	175
U.K. government bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	168	140
U.K. corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	43	35
Cash
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 2	$ 1