Investments (Equity Investments Without Readily Determinable Fair Values Assessed Under the Measurement Alternative) (Details) $ in Millions	9 Months Ended
Sep. 30, 2018 USD ($)
GroupNineMedia
Other Investment Not Readily Marketable [Line Items]
Equity investments without readily determinable fair value	$ 212
Refinery29
Other Investment Not Readily Marketable [Line Items]
Equity investments without readily determinable fair value	35
Impairment loss	$ 5
GroupNineMedia
Other Investment Not Readily Marketable [Line Items]
Ownership percentage by parent	42.00%

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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84241550&loc=SL75117539-209714

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84241550&loc=SL75117539-209714

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- Definition

The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

+ References

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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