Debt (Details 4) (USD $) In Millions, unless otherwise specified	0 Months Ended	12 Months Ended
Aug. 21, 2013	Dec. 31, 2014
Debt Conversion [Line Items]
Original debt	$ 1,170
Debt exchange fees	9
Cash consideration	280
Accrued and unpaid interest	8
3.646% Debt Due 2024 [Member]
Debt Conversion [Line Items]
New debt	439
New rate	3.646%
New due date		Feb. 15, 2024
Date of exchange		Aug. 21, 2013
3.646% Debt Due 2024 [Member] \| 7.000% Debentures Due 2016 [Member]
Debt Conversion [Line Items]
Original debt	8
Original rate	7.00%
Original due date, year		2016
3.646% Debt Due 2024 [Member] \| 5.650% Notes Due 2017 [Member]
Debt Conversion [Line Items]
Original debt	38
Original rate	5.65%
Original due date, year		2017
3.646% Debt Due 2024 [Member] \| 5.750% Notes Due 2017 [Member]
Debt Conversion [Line Items]
Original debt	70
Original rate	5.75%
Original due date, year		2017
3.646% Debt Due 2024 [Member] \| 5.700% Notes Due 2018 [Member]
Debt Conversion [Line Items]
Original debt	103
Original rate	5.70%
Original due date, year		2018
3.646% Debt Due 2024 [Member] \| 7.875% Notes Due 2019 [Member]
Debt Conversion [Line Items]
Original debt	20
Original rate	7.875%
Original due date, year		2019
3.646% Debt Due 2024 [Member] \| 6.125% Notes Due 2020 [Member]
Debt Conversion [Line Items]
Original debt	238
Original rate	6.125%
Original due date, year		2020
4.821% Debt Due 2044 [Member]
Debt Conversion [Line Items]
New debt	700
New rate	4.821%
New due date		Feb. 01, 2044
Date of exchange		Aug. 21, 2013
4.821% Debt Due 2044 [Member] \| 7.125% Debentures Due 2028 [Member]
Debt Conversion [Line Items]
Original debt	73
Original rate	7.125%
Original due date, year		2028
4.821% Debt Due 2044 [Member] \| 6.625% Debentures Due 2029 [Member]
Debt Conversion [Line Items]
Original debt	177
Original rate	6.625%
Original due date, year		2029
4.821% Debt Due 2044 [Member] \| 6.250% Debentures Due 2034 [Member]
Debt Conversion [Line Items]
Original debt	19
Original rate	6.25%
Original due date, year		2034
4.821% Debt Due 2044 [Member] \| 6.150% Debentures Due 2037 [Member]
Debt Conversion [Line Items]
Original debt	138
Original rate	6.15%
Original due date, year		2037
4.821% Debt Due 2044 [Member] \| 5.780% Notes Due 2040 [Member]
Debt Conversion [Line Items]
Original debt	$ 286
Original rate	5.78%
Original due date, year		2040

Accrued interest paid to debt holder on the existing debt at date of exchange.

No definition available.

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- Definition

The value of the financial instrument(s) that the original debt is being converted into in a noncash (or part noncash) transaction. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

+ References

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- Definition

Expiration, mandatory redemption, or due date, in CCYY-MM-DD format, of the financial instrument issued in exchange for the original debt being converted in a noncash or part noncash transaction.

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- Definition

Date the financial instrument was issued in exchange for the original debt being converted in a noncash or part noncash transaction, in CCYY-MM-DD format.

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- Definition

Dividend or interest rate associated with the financial instrument issued in exchange for the original debt being converted in a noncash or part noncash transaction. Noncash are transactions that affect recognized assets or liabilities but that do not result in cash receipts or cash payments. Part noncash refers to that portion of the transaction not resulting in cash receipts or cash payments.

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- Definition

The amount of the original debt being converted in a noncash (or part noncash) transaction. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

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- Definition

Year the original debt was scheduled to mature, in CCYY format.

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- Definition

The rate of interest that was being paid on the original debt issue that is being converted in the noncash (or part noncash) transaction. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

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- Definition

The amount of debt issuance costs that were incurred during a noncash or partial noncash transaction.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4332-108586

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4313-108586

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4304-108586

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- Definition

The total of the cash outflow during the period which has been paid to third parties in connection with debt origination, which will be amortized over the remaining maturity period of the associated long-term debt and the cost incurred directly for the issuance of equity securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 15

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585

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