Fair value portion of borrowing which can be exchanged for a specified number of another security at the option of the issuer or the holder, for example, but not limited to, the entity's common stock.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Convertible Security
-URI http://asc.fasb.org/extlink&oid=6509036

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Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ 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(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

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

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Fair value of obligations measured on a recurring basis.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a),(b)
-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

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Fair value of subordinated debt obligations including, but not limited to, subordinated loan, subordinated bond, subordinated debenture or junior debt.

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Fair Value Measurements (Financial Instruments) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Level 1 \| Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior and senior subordinated notes	$ 5,916	$ 5,984
Level 1 \| Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior and senior subordinated notes	6,030	6,390
Level 2 \| Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
4 percent Convertible Senior Notes	0	32
Level 2 \| Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
4 percent Convertible Senior Notes	0	33
Level 3 \| Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Capital leases	96	105
Level 3 \| Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Capital leases	$ 95	$ 104
4 percent Convertible Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	4.00%	4.00%	4.00%
Effective interest rate		7.30%
Capital leases
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Effective interest rate	7.00%
Convertible debt \| 4 percent Convertible Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	4.00%	4.00%	4.00%