SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Workforce Optimization (Details) $ in Millions	12 Months Ended
Dec. 31, 2019 USD ($) employee	Dec. 31, 2017 USD ($) employee	Dec. 31, 2018 USD ($)
Accounting Policies [Abstract]
Expected number of associates impacted \| employee	1,000	3,600
Estimated charges	$ 47	$ 148
Workforce optimization obligation	$ 45		$ 12

Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

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