| **Postretirement Benefits**                           | 6 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
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| **Compensation and Retirement Disclosure [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
| Postretirement Benefits                               | Postretirement BenefitsDefined Benefit PlansWe provide postretirement benefits to a substantial portion of our employees and retirees. Costs associated with postretirement benefits include pension and postretirement health care expenses for employees, retirees, surviving spouses and dependents.Generally, the pension plans are non-contributory. Our policy is to fund the pension plans in accordance with applicable U.S. and Canadian government regulations and to make additional contributions from time to time. For the three and six months ended April 30, 2015, we contributed $32 million and $62 million, respectively, and for the three and six months ended April 30, 2014, we contributed $36 million and $65 million, respectively, to our pension plans to meet regulatory funding requirements.  In August 2014, the Highway and Transportation Funding Act of 2014 ("HATFA"), including extension of pension funding interest rate relief, was signed into law.  As a result, we lowered our funding expectations. We currently anticipate additional contributions of $51 million to our pension plans during the remainder of 2015. We primarily fund other post-employment benefit ("OPEB") obligations, such as retiree medical, in accordance with a 1993 Settlement Agreement (the "1993 Settlement Agreement"), which requires us to fund a portion of the plans' annual service cost to a retiree benefit trust (the "Base Trust"). The 1993 Settlement Agreement resolved a class action lawsuit originally filed in 1992 regarding the restructuring of the Company's then applicable retiree health care and life insurance benefits. Contributions for the six months ended April 30, 2015 and 2014, as well as anticipated contributions for the remainder of 2015, are not material.Components of Net Periodic Benefit Expense Net postretirement benefits expense included in our Consolidated Statements of Operations is comprised of the following: Three Months Ended April 30, Six Months Ended April 30, Pension Benefits Health and LifeInsurance Benefits Pension Benefits Health and LifeInsurance Benefits(in millions)2015 2014 2015 2014 2015 2014 2015 2014Service cost for benefits earned during the period$3 $2 $2 $1 $6 $6 $3 $2Interest on obligation35 40 18 17 71 79 36 34Amortization of cumulative loss24 23 9 4 49 47 19 8Amortization of prior service benefit— — (1) (1) — — (2) (2)Contractual termination benefits(1) — (1) — (1) — (1) —Premiums on pension insurance4 — — — 5 — — —Expected return on assets(48) (48) (8) (8) (97) (96) (15) (16)Net postretirement benefits expense$17 $17 $19 $13 $33 $36 $40 $26Defined Contribution Plans and Other Contractual ArrangementsOur defined contribution plans cover a substantial portion of domestic salaried employees and certain domestic represented employees. The defined contribution plans contain a 401(k) feature and provide most participants with a matching contribution from the Company. The Company deposits the matching contribution annually. Many participants covered by the plans receive annual Company contributions to their retirement accounts based on an age-weighted percentage of the participant's eligible compensation for the calendar year. Defined contribution expense pursuant to these plans was $8 million and $17 million in the three and six months ended April 30, 2015, respectively, and $7 million and $15 million for the three and six months ended April 30, 2014, respectively. In accordance with the 1993 Settlement Agreement, an independent Retiree Supplemental Benefit Trust (the "Supplemental Trust") was established. The Supplemental Trust, and the benefits it provides to certain retirees pursuant to a certain Retiree Supplemental Benefit Program under the 1993 Settlement Agreement ("Supplemental Benefit Program"), is not part of the Company's consolidated financial statements. The Company's contingent profit sharing obligations under a certain Supplemental Benefits Trust Profit Sharing Plan ("Supplemental Benefit Profit Sharing Plan") will continue until certain funding targets defined by the 1993 Settlement Agreement are met. We have recorded no profit sharing accruals based on the operating performance of the entities that are included in the determination of qualifying profits. For more information, see Note 11, Commitments and Contingencies, for a discussion of pending arbitration regarding the Supplemental Benefit Profit Sharing Plan. |

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| - Definition
The entire disclosure for pension and other postretirement benefits.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6414718&loc=d3e28014-114942Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e2410-114920Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 80 -Section 50 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=35742057&loc=SL14450702-114947Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 60 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6414199&loc=d3e39622-114963Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 60 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6414203&loc=d3e39675-114964
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