Risk Management Effect of Derivative Contracts on the Income Statement (Details) - Designated as Hedging Instrument [Member] - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain/(loss) recognized in OCI on derivative (effective portion)(a)	$ 145	$ 227	$ (164)
Gain/(loss) reclassified from Accumulated OCI into income (effective portion)(b)	(109)	268	183
Gain/(loss) recognized in income on derivative (ineffective portion and amount excluded from effectiveness testing)	(65)	11	(12)
Loss to be reclassified within twelve months	165
Net Investment Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain/(loss) reclassified from Accumulated OCI into income (effective portion)(b)	26	0	0
Gain/(loss) recognized in income on derivative (ineffective portion and amount excluded from effectiveness testing)	0	0	0
Interest rate contract \| Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain/(loss) recognized in OCI on derivative (effective portion)(a)	3	0	(3)
Interest rate contract \| Earnings from Equity Investments [Member] \| Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Discontinuation of Cash Flow Hedge Due to Forecasted Transaction Probable of Not Occurring, Net	(3)
Interest rate contract \| Interest Expense [Member] \| Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain/(loss) reclassified from Accumulated OCI into income (effective portion)(b)	(4)	(5)	(4)
Gain/(loss) recognized in income on derivative (ineffective portion and amount excluded from effectiveness testing)	0	0	0
Interest rate contract \| Costs of sales \| Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Inventory Write-down	21
Energy commodity derivative contracts(a) \| Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain/(loss) recognized in OCI on derivative (effective portion)(a)	201	37	(182)
Energy commodity derivative contracts(a) \| Revenues—Natural gas sales \| Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain/(loss) reclassified from Accumulated OCI into income (effective portion)(b)	(29)	18	23
Gain/(loss) recognized in income on derivative (ineffective portion and amount excluded from effectiveness testing)	0	0	0
Energy commodity derivative contracts(a) \| Revenues—Product sales and other \| Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain/(loss) reclassified from Accumulated OCI into income (effective portion)(b)	(30)	55	233
Gain/(loss) recognized in income on derivative (ineffective portion and amount excluded from effectiveness testing)	(65)	11	(12)
Energy commodity derivative contracts(a) \| Costs of sales \| Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain/(loss) reclassified from Accumulated OCI into income (effective portion)(b)	21	14	(26)
Gain/(loss) recognized in income on derivative (ineffective portion and amount excluded from effectiveness testing)	0	0	0
Currency Swap [Member] \| Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain/(loss) recognized in OCI on derivative (effective portion)(a)	(59)	190	21
Currency Swap [Member] \| Other Nonoperating Income (Expense) [Member] \| Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain/(loss) reclassified from Accumulated OCI into income (effective portion)(b)	(67)	186	(43)
Gain/(loss) recognized in income on derivative (ineffective portion and amount excluded from effectiveness testing)	$ 0	$ 0	$ 0

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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The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

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The portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments representing (a) the amount of the hedge ineffectiveness and (b) the amount, if any, excluded from the assessment of hedge effectiveness.

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The amount of net gain (loss) reclassified into earnings in the period when cash flow hedge is discontinued because it is probable that the original forecasted transactions will not occur by the end of the original period or an additional two month time period.

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Amount of loss from reductions in inventory due to subsequent measurement adjustments, including, but not limited to, physical deterioration, obsolescence, or changes in price levels.

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