| **Leases (Tables)**                                                                                          | 12 Months Ended                                                                                                                                                                                                                                          |
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| **Leases [Abstract]**                                                                                        |                                                                                                                                                                                                                                                     |
| Minimum payments for operating leases having initial or remaining non-cancelable terms in excess of one year | At December 31, 2012, minimum payments for operating leases having initial or remaining non-cancelable terms in excess of one year were as follows: (Millions of dollars) 2013$14201413201512201610201710Thereafter36Total$95   |

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| - Details**Name:**us-gaap_LeasesAbstract**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
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| - Definition
Tabular disclosure of future minimum payments required in the aggregate and for each of the five succeeding fiscal years for operating leases having initial or remaining noncancelable lease terms in excess of one year and the total minimum rentals to be received in the future under noncancelable subleases as of the balance sheet date.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41502-112717
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