Fair Value Measurements (Textuals) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2014	Dec. 31, 2016	Dec. 31, 2015
Money Market Funds, at Carrying Value		$ 320	$ 2
Deferred Compensation Plan Assets		6	5
Obligations, Fair Value Disclosure		(11)	(12)
Assets, Fair Value Disclosure		299	370
Quoted Prices In Active Markets for Identical Assets or Liabilities, Fair Value Inputs (Level 1) [Member]
Money Market Funds, at Carrying Value		320	2
Deferred Compensation Plan Assets		6	5
Obligations, Fair Value Disclosure		(11)	(12)
Assets, Fair Value Disclosure		324	3
Fair Value, Inputs, Level 2 [Member]
Money Market Funds, at Carrying Value		0	0
Deferred Compensation Plan Assets		0	0
Obligations, Fair Value Disclosure		0	0
Assets, Fair Value Disclosure		50	675
Fair Value, Inputs, Level 3 [Member]
Money Market Funds, at Carrying Value		0	0
Deferred Compensation Plan Assets		0	0
Obligations, Fair Value Disclosure		0	0
Financial and Nonfinancial Liabilities, Fair Value Disclosure		(75)	(308)
Equity Securities [Member]
Available-for-sale Securities		9	8
Proceeds from Sale of Available-for-sale Securities	$ 39
Equity Securities [Member] \| Quoted Prices In Active Markets for Identical Assets or Liabilities, Fair Value Inputs (Level 1) [Member]
Available-for-sale Securities		9	8
Equity Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Available-for-sale Securities		0	0
Equity Securities [Member] \| Fair Value, Inputs, Level 3 [Member]
Available-for-sale Securities		0	0
Swap [Member]
Derivative Assets		50	675
Swap [Member] \| Quoted Prices In Active Markets for Identical Assets or Liabilities, Fair Value Inputs (Level 1) [Member]
Derivative Assets		0	0
Swap [Member] \| Fair Value, Inputs, Level 2 [Member]
Derivative Assets		50	675
Swap [Member] \| Fair Value, Inputs, Level 3 [Member]
Derivative Assets		0	0
Commodity Option [Member]
Derivative Liability		(75)	(308)
Commodity Option [Member] \| Quoted Prices In Active Markets for Identical Assets or Liabilities, Fair Value Inputs (Level 1) [Member]
Derivative Assets		0	0
Commodity Option [Member] \| Fair Value, Inputs, Level 2 [Member]
Derivative Assets		0	0
Commodity Option [Member] \| Fair Value, Inputs, Level 3 [Member]
Derivative Liability		$ (75)	$ (308)

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Carrying amount as of the balance sheet date of assets held under deferred compensation agreements.

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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Fair value of obligations measured on a recurring basis.

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Fair value of financial and nonfinancial obligations.

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Investment in short-term money-market instruments (such as commercial paper, banker's acceptances, repurchase agreements, government securities, certificates of deposit, and so forth) which are highly liquid (that is, readily convertible to known amounts of cash) and so near their maturity that they present an insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify as cash equivalents by definition. Original maturity means an original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months.

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The cash inflow associated with the sale of debt and equity securities classified as available-for-sale securities.

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