Long-term Debt (Schedule of Long-term Debt) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Total	$ 6,848us-gaap_DebtAndCapitalLeaseObligations	$ 7,134us-gaap_DebtAndCapitalLeaseObligations
Less amounts due in one year	50	73
Long-term debt	6,798	7,061
Senior Notes [Member] \| Senior Notes, 5.95 Percent due 2012 [Member]
Debt Instrument [Line Items]
Stated interest rate on debt	5.95%
Senior Notes [Member] \| Senior Notes, 5.15% due 2013 [Member]
Debt Instrument [Line Items]
Stated interest rate on debt	5.15%
Senior Notes [Member] \| Senior Notes, 4.95% due 2013 [Member]
Debt Instrument [Line Items]
Stated interest rate on debt	4.95%
Senior Notes [Member] \| Senior Notes, 5.50% due 2016 [Member]
Debt Instrument [Line Items]
Stated interest rate on debt	5.50%
Total	352	353
Senior Notes [Member] \| Senior Notes, 6.35% due 2017 [Member]
Debt Instrument [Line Items]
Stated interest rate on debt	6.35%
Total	607	610
Senior Notes [Member] \| Senior Notes, 6.00% due 2018 [Member]
Debt Instrument [Line Items]
Stated interest rate on debt	6.00%
Total	498	498
Senior Notes [Member] \| Senior Notes, 9.625% due 2019 [Member]
Debt Instrument [Line Items]
Stated interest rate on debt	9.625%
Total	1,018	1,021
Senior Notes [Member] \| Senior Notes, 5.125% due 2020 [Member]
Debt Instrument [Line Items]
Stated interest rate on debt	5.125%
Total	798	798
Senior Notes [Member] \| Senior Notes, 4.50% due 2022 [Member]
Debt Instrument [Line Items]
Stated interest rate on debt	4.50%
Total	715	747
Senior Notes [Member] \| Senior Notes, 6.50 Percent due 2036 [Member]
Debt Instrument [Line Items]
Stated interest rate on debt	6.50%
Total	556	595
Senior Notes [Member] \| Senior Notes, 6.80% due 2037 [Member]
Debt Instrument [Line Items]
Stated interest rate on debt	6.80%
Total	298	298
Senior Notes [Member] \| Senior Notes, 7.00% due 2038 [Member]
Debt Instrument [Line Items]
Stated interest rate on debt	7.00%
Total	497	497
Senior Notes [Member] \| Senior Notes, 9.875% due 2039 [Member]
Debt Instrument [Line Items]
Stated interest rate on debt	9.875%
Total	247	247
Senior Notes [Member] \| Senior Notes, 6.75% due 2040 [Member]
Debt Instrument [Line Items]
Stated interest rate on debt	6.75%
Total	596	596
Senior Notes [Member] \| Senior Notes, 5.95% due 2042 [Member]
Debt Instrument [Line Items]
Stated interest rate on debt	5.95%
Total	478	545
Secured Borrowings [Member] \| Secured Borrowing, 4.82% [Member]
Debt Instrument [Line Items]
Stated interest rate on debt	4.82%
Total	12	102
Capital and Other Lease Obligations [Member]
Debt Instrument [Line Items]
Total	136	153
Other Long-term Debt [Member]
Debt Instrument [Line Items]
Total	$ 40	$ 74

Sum of the carrying values as of the balance sheet date of all debt, including all short-term borrowings, long-term debt, and capital lease obligations.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.16)

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.13,16)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

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Amount of long-term debt and capital lease obligation due after one year or beyond the normal operating cycle, if longer.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

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

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 6

-Section H

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Amount of long-term debt and capital leases due within one year or the normal operating cycle, if longer.

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