Investments - Schedule of Total Gains and Losses on Equity Securities (Detail) - USD ($) $ in Millions	3 Months Ended
Sep. 30, 2018	Sep. 30, 2017
Investments Schedule [Abstract]
Total gains (losses) recognized on equity securities	$ 15	$ (19)
Less: Gains (losses) recognized on equity securities sold	0	6
Unrealized gains (losses) recognized on equity securities held at end of period	$ 15	$ (25)

No definition available.

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=84241550&loc=SL75117546-209714

+ Details

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- Definition

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

+ References

+ Details

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- Definition

The difference between the carrying value and the sale price of equity securities, not separately or otherwise categorized as trading or available-for-sale. This element includes investments in which the entity holds a small ownership stake (generally, less than 20% of the shares outstanding) and cannot exert significant influence.

+ References

No definition available.

+ Details

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