Summary of Significant Accounting Policies (Major Customers and Credit Risk) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Concentration Risk [Line Items]
Concentration percentage	100.00%us-gaap_ConcentrationRiskPercentage1	100.00%us-gaap_ConcentrationRiskPercentage1	100.00%us-gaap_ConcentrationRiskPercentage1
Accounts receivable, current	$ 3,015us-gaap_ReceivablesNetCurrent	$ 3,351us-gaap_ReceivablesNetCurrent
Increase (decrease) in accounts receivable	(78)	12	705
Depreciation	1,300us-gaap_Depreciation	1,300us-gaap_Depreciation	1,200us-gaap_Depreciation
Accounts Receivable [Member] \| Customer Concentration Risk [Member] \| Petroleos de Venezuela, S.A. [Member]
Concentration Risk [Line Items]
Accounts receivable, current	66
Gain (loss) on sale of bonds		(58)
Increase (decrease) in accounts receivable		(127)
Bond face amount		127
Accounts Receivable [Member] \| Customer Concentration Risk [Member] \| Petroleos Mexicanos [Member]
Concentration Risk [Line Items]
Accounts receivable, current	$ 142
Accounts Receivable [Member] \| Latin America [Member] \| Geographic Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration percentage	26.00%
Sales Revenue, Net [Member] \| Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration percentage	10.00%	10.00%	10.00%

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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

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The increase (decrease) during the reporting period in amount due within one year (or one business cycle) from customers for the credit sale of goods and services.

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The total amount due to the entity within one year of the balance sheet date (or one operating cycle, if longer) from outside sources, including trade accounts receivable, notes and loans receivable, as well as any other types of receivables, net of allowances established for the purpose of reducing such receivables to an amount that approximates their net realizable value.

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Amount of investments in debt securities classified as trading.

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This item represents the gain (loss) realized during the period from the sale of trading securities.

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