The estimated net amount of existing gains or losses on cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months.

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Risk Management - Effect on Income Statement Locations (Details) - Derivatives in cash flow hedging relationships - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Derivative [Line Items]
Cash flow hedge loss to be reclassified within twelve months			$ 69
Derivatives designated as hedging instruments
Derivative [Line Items]
Gain/(loss) recognized in OCI on derivative	$ 26	$ (113)	(171)	$ (172)
Gain/(loss) reclassified from Accumulated OCI into income	(53)	(15)	(46)	(101)
Derivatives designated as hedging instruments \| Energy commodity derivative contracts
Derivative [Line Items]
Gain/(loss) recognized in OCI on derivative	96	(109)	(74)	(160)
Derivatives designated as hedging instruments \| Interest rate contracts
Derivative [Line Items]
Gain/(loss) recognized in OCI on derivative	(1)	0	(2)	3
Derivatives designated as hedging instruments \| Foreign currency contracts
Derivative [Line Items]
Gain/(loss) recognized in OCI on derivative	(69)	(4)	(95)	(15)
Revenues—Natural gas sales \| Derivatives designated as hedging instruments \| Energy commodity derivative contracts
Derivative [Line Items]
Gain/(loss) reclassified from Accumulated OCI into income	11	(4)	16	(9)
Revenues—Product sales and other \| Derivatives designated as hedging instruments \| Energy commodity derivative contracts
Derivative [Line Items]
Gain/(loss) reclassified from Accumulated OCI into income	(2)	(3)	(1)	(40)
Cost of sales \| Derivatives designated as hedging instruments \| Energy commodity derivative contracts
Derivative [Line Items]
Gain/(loss) reclassified from Accumulated OCI into income	(3)	2	8	3
Write-Down of Hedged Inventory \| Derivatives designated as hedging instruments \| Energy commodity derivative contracts
Derivative [Line Items]
Gain/(loss) reclassified from Accumulated OCI into income			12
Earnings from equity investments \| Derivatives designated as hedging instruments \| Energy commodity derivative contracts
Derivative [Line Items]
Loss due to forecasted transactions being probable of not occurring				(3)
Earnings from equity investments \| Derivatives designated as hedging instruments \| Interest rate contracts
Derivative [Line Items]
Gain/(loss) reclassified from Accumulated OCI into income	0	0	2	(5)
Other, net \| Derivatives designated as hedging instruments \| Foreign currency contracts
Derivative [Line Items]
Gain/(loss) reclassified from Accumulated OCI into income	$ (59)	$ (10)	$ (71)	$ (50)