Financial Instruments Narrative (Details) bbl in Millions, $ in Millions		9 Months Ended	12 Months Ended
		Sep. 30, 2019 USD ($) bbl	Dec. 31, 2018 USD ($) bbl
Investment Segment
Derivative [Line Items]
Fair value derivative instruments with credit risk related contingent features in a liability position		$ 108	$ 0
Not designated as hedging instrument | Commodity contracts not considered probable of settlement | Energy Segment
Derivative [Line Items]
Volume of derivatives (barrels) | bbl		6	2
Not designated as hedging instrument | RINs contracts | Energy Segment
Derivative [Line Items]
Number of derivatives | bbl		38
Other assets | Not designated as hedging instrument | Investment Segment
Derivative [Line Items]
Asset Derivatives, Gross	[1]	$ 188	$ 651
Derivative contracts, at fair value (asset)		133	517	[1],[2]
Other assets | Not designated as hedging instrument | Energy Segment
Derivative [Line Items]
Asset Derivatives, Gross	[1]	17	8
Derivative contracts, at fair value (asset)		16	7
Other assets | Not designated as hedging instrument | Commodity contracts | Investment Segment
Derivative [Line Items]
Asset Derivatives, Gross		$ 0	$ 7	[1]

[1] Net asset derivatives are classified within other assets in our condensed consolidated balance sheets.

[2] Excludes netting of cash collateral received and posted. The total collateral posted at September 30, 2019 and December 31, 2018 was $314 million and $0 million, respectively, across all counterparties, which are included in cash held at consolidated affiliated partnerships and restricted cash in the condensed consolidated balance sheets.