| **Benefit Plans (Tables)**                            | 3 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
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| **Compensation and Retirement Disclosure [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
| Components of net periodic cost (benefit)             | Net Periodic Cost (Benefit)Three months ended March 31   (In millions)2013 2012Pension cost (benefit)   Service cost$3 $3Interest cost on projected benefit obligation30 34Expected return on plan assets(45) (43)Amortization of net actuarial (gain) loss12 10Net periodic pension cost (benefit)$— $4    Postretirement cost (benefit)   Amortization of prior service credit$(4) $(4)Net periodic postretirement cost (benefit)$(4) $(4) |

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| - Definition
Tabular 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.
+ References
Reference 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
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