| **Accumulated Other Comprehensive Income/(Loss) (Tables)**               | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
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| **Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| Schedule of Accumulated other comprehensive income/(loss)                | Comprehensive income/(loss) and its components are presented in the Consolidated Statements of Comprehensive Income.  Changes in Accumulated other comprehensive income/(loss), net of tax, included in the Consolidated Statements of Changes in Stockholder's Equity, consisted of the following:(Millions of dollars)Foreign currency translation Derivative financial instruments Total      Balance at December 31, 2012$184 $(8) $176Other comprehensive income/(loss) before reclassifications(62) (1) (63)Amounts reclassified from accumulated other comprehensive (income)/loss— 4 4Other comprehensive income/(loss)(62) 3 (59)Balance at December 31, 2013$122 $(5) $117Other comprehensive income/(loss) before reclassifications(481) (4) (485)Amounts reclassified from accumulated other comprehensive (income)/loss— 4 4Other comprehensive income/(loss)(481) — (481)Balance at December 31, 2014$(359) $(5) $(364)Other comprehensive income/(loss) before reclassifications(538) 2 (536)Amounts reclassified from accumulated other comprehensive (income)/loss— 3 3Other comprehensive income/(loss)(538) 5 (533)Balance at December 31, 2015$(897) $— $(897)       |
| Reclassifications out of Accumulated other comprehensive income/(loss)   | The effect of the reclassifications out of Accumulated other comprehensive income/(loss) on the Consolidated Statements of Profit during the years ended December 31, 2015, 2014 and 2013 was as follows:(Millions of dollars)        Classification of income (expense) 2015 2014 2013Cross currency contractsOther income (expense) $1 $— $—Interest rate contractsInterest expense (6) (6) (6)Reclassifications before tax  (5) (6) (6)Tax (provision) benefit  2 2 2Total reclassifications from Accumulated other comprehensive income/(loss) $(3) $(4) $(4)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |

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| - References
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| - Definition
Tabular disclosure of information about items reclassified out of accumulated other comprehensive income (loss).
+ References
No definition available.
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| - Definition
Tabular disclosure of the components of accumulated other comprehensive income (loss).
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=36458714&loc=SL7669686-108580
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