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Summary of Significant Accounting Policies - Investments (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Summary of Significant Accounting Policies
Equity method investments	$ 257	$ 127
Investments without readily determinable fair values	83	87
Redeemable preferred stock	66	55
Investments in unconsolidated entities	$ 406	$ 269

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Total investments in (A) an entity in which the entity has significant influence, but does not have control, (B) subsidiaries that are not required to be consolidated and are accounted for using the equity and or cost method, and (C) an entity in which the reporting entity shares control of the entity with another party or group. Includes long-term advances receivable from a party that is affiliated with the reporting entity by means of direct or indirect ownership.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.12)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Amount of investment in equity security without readily determinable fair value.

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Amount of investment in redeemable preferred stock measured at fair value with change in fair value recognized in net income (FV-NI).

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