Derivatives (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
1.125% Convertible Notes
Derivative [Line Items]
Percentage of contractual interest rate on Notes	1.125%
1.125% Call Option
Derivative [Line Items]
Percentage of contractual interest rate on Call Option	1.125%
1.125% Conversion Option derivative liability
Derivative [Line Items]
Percentage of contractual interest rate on Call Option	1.125%
Current assets \| 1.125% Call Option
Derivative [Line Items]
Derivative assets	$ 0	$ 267
Non-current assets \| 1.125% Call Option
Derivative [Line Items]
Derivative assets	181	0
Current liabilities \| 1.125% Conversion Option derivative liability
Derivative [Line Items]
Derivative liabilities	0	267
Non-current liabilities \| 1.125% Conversion Option derivative liability
Derivative [Line Items]
Derivative liabilities	$ 181	$ 0

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

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

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
-Paragraph 4B
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
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-Section 50
-Paragraph 4D
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=64830801&loc=SL51823488-111719

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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- Definition

Fixed interest rate related to the interest rate derivative.

+ References

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