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Carrying value as of the balance sheet date of obligations incurred through that date and payable for advertising of the entity's goods and services. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Period between issuance and maturity of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Total of the carrying values as of the balance sheet date of obligations incurred through that date and payable for obligations related to services received from employees, such as accrued salaries and bonuses, payroll taxes and fringe benefits. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Term of lessee's operating lease renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

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The cash inflow from a debt initially having maturity due after one year or beyond the operating cycle, if longer.

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) $ in Millions	1 Months Ended	12 Months Ended
	Apr. 30, 2020 USD ($)	Dec. 31, 2020 USD ($) segment	Dec. 31, 2019 USD ($) segment	Dec. 31, 2018 USD ($) segment	Dec. 31, 2017 USD ($)
Accounting Policies [Line Items]
Proceeds from the issuance of long-term debt	$ 4,100	$ 4,108	$ 0	$ 0
Equity		4,893	5,933	$ 8,785	$ 11,261
Accrued performance advertising liabilities		156	333
Accrued compensation liabilities		$ 333	$ 344
Number of operating segments \| segment		4	4	6
Number of reportable segments \| segment		1
Cumulative effect of adoption of accounting standards updates
Accounting Policies [Line Items]
Equity			$ (3)		189
Retained Earnings
Accounting Policies [Line Items]
Equity		$ 23,288	23,232	$ 18,367	13,939
Retained Earnings \| Cumulative effect of adoption of accounting standards updates
Accounting Policies [Line Items]
Equity			$ (3)		430
Retained Earnings \| Cumulative effect of adoption of accounting standards updates \| Accounting Standards Update 2014-09
Accounting Policies [Line Items]
Equity					$ 189
Maximum
Accounting Policies [Line Items]
Term of available-for-sale debt securities		5 years
Renewal terms		9 years