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Debt and Credit Facility - Convertible Senior Notes (Narrative) (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | Jul. 31, 2010
Debt Instrument [Line Items] |  |  |  |
Proceeds from convertible note hedges | $ 0 | $ 956 | $ 784 |
Payments to settle warrants | $ 0 | 469 | $ 3,865 |
Convertible Senior Notes Due May 2016 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Debt Instrument, Face Amount |  |  |  | $ 1,300
Repayments of Convertible Debt |  | 285 |  |
Conversion value paid in excess of principal |  | 956 |  |
Proceeds from convertible note hedges |  | $ 956 |  |

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- Definition Payment to Settle Warrants Related to Convertible Notes + References No definition available. + Details
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- Definition Amount of a favorable spread to a debt holder between the amount of debt being converted and the value of the securities received upon conversion. This is an embedded conversion feature of convertible debt issued that is in-the-money at the commitment date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21538-112644 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Beneficial Conversion Feature -URI http://asc.fasb.org/extlink&oid=6505963 + Details
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- Definition Face (par) amount of debt instrument at time of issuance. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400 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=64930785&loc=d3e28551-108399 + Details
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- Definition The cash inflow from a financial contract that meets the hedge criteria as either cash flow hedge, fair value hedge or hedge of net investment in foreign operations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 27 -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3581-108585 + Details
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- Definition The cash outflow from the repayment of a long-term debt instrument which can be exchanged for a specified amount of another security, typically the entity's common stock, at the option of the issuer or the holder. + 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 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3291-108585 + Details
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