| **Postretirement Benefits**                           | 6 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|-------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
||
| **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, 2016, we contributed $21 million and $40 million, respectively, and for the three and six months ended April 30, 2015, we contributed $32 million and $62 million, respectively, to our pension plans to meet regulatory funding requirements.  We expect to contribute approximately $57 million to our pension plans during the remainder of 2016. 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 our then applicable retiree health care and life insurance benefits. Contributions for the three and six months ended April 30, 2016 and 2015, as well as anticipated contributions for the remainder of 2016, are not material.Components of Net Periodic Benefit ExpenseNet periodic benefit 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)2016 2015 2016 2015 2016 2015 2016 2015Service cost for benefits earned during the period$3 $3 $2 $2 $5 $6 $3 $3Interest on obligation29 35 15 18 59 71 30 36Amortization of cumulative loss26 24 8 9 52 49 16 19Amortization of prior service benefit— — (1) (1) — — (1) (2)Contractual termination benefits2 (1) — (1) 2 (1) — (1)Premiums on pension insurance4 4 — — 8 5 — —Expected return on assets(42) (48) (7) (8) (84) (97) (13) (15)Net periodic benefit expense$22 $17 $17 $19 $42 $33 $35 $40In 2016, we changed the approach utilized to estimate the service cost and interest cost components of net periodic benefit cost for our major defined benefit postretirement plans.  Historically, we estimated the service cost and interest cost components using a single weighted average discount rate derived from the yield curve used to measure the benefit obligation at the beginning of the period.  In 2016, we are using a spot rate approach for the estimation of service and interest cost for our major plans by applying specific spot rates along the yield curve to the relevant projected cash flows, to provide a better estimate of service and interest costs. Interest on the obligation as reported above is $9 million and $4 million lower in the three months ended April 30, 2016 for pension and for health and life insurance, respectively, and $18 million and $8 million lower in the six months ended April 30, 2016 for pension and for health and life insurance, respectively, as a result of using the spot rate approach compared to the historical approach.Defined 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. We deposit 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 $15 million in the three and six months ended April 30, 2016, respectively, and $8 million and $17 million in the three and six months ended April 30, 2015, 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 our consolidated financial statements. Our contingent profit sharing obligations under a certain Supplemental Benefit Trust Profit Sharing Plan ("Supplemental Benefit Trust 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 on pending arbitration regarding the Supplemental Benefit Trust Profit Sharing Plan, see Note 11, Commitments and Contingencies. |

| X                                                                                                                                                                                                                     |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - References
No definition available.
+ Details**Name:**us-gaap_CompensationAndRetirementDisclosureAbstract**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - 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 80 -Section 50 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450702-114947Reference 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=65897934&loc=d3e2410-114920Reference 3: 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=d3e39675-114964Reference 4: 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=49170846&loc=d3e28014-114942Reference 5: 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=66047640&loc=d3e39622-114963
+ Details**Name:**us-gaap_PensionAndOtherPostretirementBenefitsDisclosureTextBlock**Namespace Prefix:**us-gaap_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |