Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016
Net cash provided by (used in) operating activities included:
Interest paid (net of amounts capitalized)	$ (269)	$ (243)
Income taxes paid to taxing authorities	(101)	(68)
Noncash investing activities:
Changes in asset retirement costs	(94)	3
Asset retirement obligations assumed by buyer	14	86
Capital Expenditures Incurred but Not yet Paid	207	0
Receivable Related To Disposal Of Assets	$ 745	$ 0

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Receivable Related To Disposal Of Assets, not yet collected

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Amount of increase (decrease) in asset retirement obligations.

+ References

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Future cash outflow to pay for purchases of fixed assets that have occurred.

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The amount of cash paid during the current period to foreign, federal, state, and local authorities as taxes on income, net of any cash received during the current period as refunds for the overpayment of taxes.

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Amount of cash paid, after deduction of cash paid for capitalized interest, for interest. Includes, but is not limited to, payment to settle zero-coupon bond for accreted interest of debt discount and debt instrument with insignificant coupon interest rate in relation to effective interest rate of borrowing attributable to accreted interest of debt discount.

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