Restructuring Changes in liabilities recorded related to contract termination costs and ARO (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2017	Dec. 31, 2016
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	$ 17	$ 31
Restructuring Reserve, Period Increase (Decrease)	(14)
Contract Termination [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	11	18
Restructuring Reserve, Period Increase (Decrease)	(7)
Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	6	$ 13
Restructuring Reserve, Period Increase (Decrease)	$ (7)

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

+ Details

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- Definition

Carrying amount (including both current and noncurrent portions of the accrual) as of the balance sheet date pertaining to a specified type of cost associated with exit from or disposal of business activities or restructuring pursuant to a duly authorized plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB TOPIC 5.P.4(b))
-URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140904-122747

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869

+ Details

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- Definition

Amount of increase (decrease) in the accrual for restructuring costs.

+ References

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- Details

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