Investments - Unrealized gains (losses) recognized in income (Details) - Consolidated Entity Excluding Variable Interest Entities (VIE) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Gain (Loss) on Securities [Line Items]
Debt Securities, Trading, Unrealized Gain (Loss)	$ (79)	$ 16	$ (118)	$ 75
Equity Securities, FV-NI, Unrealized Gain (Loss)	(2)	2	2	15
Related Party
Gain (Loss) on Securities [Line Items]
Debt Securities, Trading, Unrealized Gain (Loss)	$ (12)	$ 2	$ (18)	$ 2

Amount of unrealized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in net income (trading).

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27357-111563

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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

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

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+ References

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