SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Reconciliation of Cash and Cash Equivalents and Restricted Cash and Cash Equivalents (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Cash and cash equivalents	$ 10,562	$ 6,312	$ 2,624
Restricted cash and cash equivalents included in "Other current assets"	20	20	21
Total cash and cash equivalents and restricted cash and cash equivalents as shown in the Consolidated Statements of Cash Flows	$ 10,582	$ 6,332	$ 2,645	$ 2,563