|**Benefit Plans (Tables)**                            | 9 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|----------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|
|**Compensation and Retirement Disclosure [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
|Components of net periodic cost (benefit)             | Net Periodic Cost (Benefit)Periods ended September 30Three MonthsNine Months(In millions)2013201220132012Pension cost (benefit)Service cost$3$3$9$9Interest cost on projected benefit obligation303490101Expected return on plan assets(45)(43)(135)(128)Amortization of net actuarial (gain) loss10103429Settlement loss3—3—Net periodic pension cost (benefit)$1$4$1$11Postretirement cost (benefit)Interest cost on projected benefit obligation$—$1$1$2Amortization of prior service credit(4)(4)(13)(13)Amortization of net actuarial (gain) loss1—1—Net periodic postretirement cost (benefit)$(3)$(3)$(11)$(11)
|                                                     
|                                                      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
|Periods ended September 30                            | Three Months                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|(In millions)                                         | 2013                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Pension cost (benefit)                                |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
|Service cost                                          | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Interest cost on projected benefit obligation         | 30                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Expected return on plan assets                        | (45                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|Amortization of net actuarial (gain) loss             | 10                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Settlement loss                                       | 3                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Net periodic pension cost (benefit)                   | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|                                                      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
|Postretirement cost (benefit)                         |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
|Interest cost on projected benefit obligation         | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Amortization of prior service credit                  | (4                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Amortization of net actuarial (gain) loss             | 1                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Net periodic postretirement cost (benefit)            | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     

X- Details**Name:**
                    us-gaap_CompensationAndRetirementDisclosureAbstract**Namespace Prefix:**
                    us-gaap_**Data Type:**
                    xbrli:stringItemType**Balance Type:**
                    na**Period Type:**
                    duration X- DefinitionTabular disclosure of the components of net benefit costs for pension plans and/or other employee benefit plans including service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) recognized due to settlements or curtailments.+ ReferencesReference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920+ Details**Name:**
                    us-gaap_ScheduleOfNetBenefitCostsTableTextBlock**Namespace Prefix:**
                    us-gaap_**Data Type:**
                    nonnum:textBlockItemType**Balance Type:**
                    na**Period Type:**
                    duration