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|**DERIVATIVE INSTRUMENTS (Tables)**                                                                       | 6 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
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|**DERIVATIVE INSTRUMENTS [Abstract]**                                                                     | Â                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Classification of derivative assets and liabilities in the Consolidated Balance Sheets                    | June 30December 31June 30201120102010Derivatives designated as hedging instrumentsAssetsDerivative instruments$.3$.4$.1Other - noncurrent-1.0-$.3$1.4$.1LiabilitiesDerivative instruments$.8$2.2$1.6Other - noncurrent-3.24.7$.8$5.4$6.3June 30December 31June 30201120102010Derivatives not designated as hedging instrumentsAssetsDerivative instruments$36.3$48.7$44.3Other - noncurrent11.417.214.0$47.7$65.9$58.3LiabilitiesDerivative instruments$56.5$80.7$86.5Other - noncurrent9.116.121.6$65.6$96.8$108.1
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|Derivatives designated as hedging instruments                                                             |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Assets                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Derivative instruments                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Other - noncurrent                                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
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|Liabilities                                                                                               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Derivative instruments                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Other - noncurrent                                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
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|Derivatives not designated as hedging instruments                                                         |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Assets                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Derivative instruments                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Other - noncurrent                                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
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|Liabilities                                                                                               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Derivative instruments                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Other - noncurrent                                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
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|Pretax gain (loss) recognized in Consolidated Statements of Income - cash flow hedges                     | Three months endedJune 30Six months endedJune 302011201020112010Pretax loss recognized in other comprehensive income$3.5$4.3$3.3$7.3Three months endedJune 30Six months endedJune 30Location2011201020112010Operating revenues$.1$.6$1.4$1.0Operating and maintenance.2.3.5.6$.3$.9$1.9$1.6                                                                                                                                                                                                                        
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|Pretax loss recognized in other comprehensive income                                                      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
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|Location                                                                                                  |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Operating revenues                                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Operating and maintenance                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
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|Pretax gain (loss) recognized in Consolidated Statements of Income - derivatives not designated as hedges | Three months endedJune 30Six months endedJune 30Location2011201020112010Operating revenues$(4.0)$(.4)$(4.2)$(1.4)Operating and maintenance-.2(.1)(.7)$(4.0)$(.2)$(4.3)$(2.1)                                                                                                                                                                                                                                                                                                                                       
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|Location                                                                                                  |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Operating revenues                                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Operating and maintenance                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
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X- DefinitionTabular disclosure of the location and amount of gains and losses reported in the statement of financial performance, or when applicable, the statement of financial position. For example,  (a) gains and losses recognized in the income statement on derivative instruments designated and qualifying as hedging instruments in fair value hedges and related hedged items designated and qualifying in fair value hedges and (b) gains and losses initially recognized in other comprehensive income on derivative instruments designated and qualifying as cash flow hedges.+ ReferencesReference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 205G -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.  This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -URI http://asc.fasb.org/extlink&oid=6935481&loc=SL5624171-113959Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6935481&loc=SL5618551-113959Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 44C -Subparagraph b -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.  This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.+ Details**Name:**
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                    duration X- DefinitionTabular disclosure of the location and fair value amounts of derivative instruments (and nonderivative instruments that are designated and qualify as hedging instruments) reported in the statement of financial position.+ ReferencesReference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4B -URI http://asc.fasb.org/extlink&oid=6935481&loc=SL5624163-113959Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 205G -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.  This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 44C -Subparagraph a -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.  This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.+ Details**Name:**
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                    duration X- DefinitionTabular disclosure for other derivative instruments not designated as hedging instruments of (a) the location and amount of gains and losses reported in the statement of financial performance and (b) the location and fair value amounts of the instruments reported in the statement of financial position.+ ReferencesReference 1: http://www.xbrl.org/2003/role/presentationRef -Topic 815 -SubTopic 10 -Publisher FASB -Number  -Article  -Subparagraph (e) -Name Accounting Standards Codification -Paragraph 4C -Section 50 -URI http://asc.fasb.org/extlink&oid=6935481&loc=SL5624171-113959+ Details**Name:**
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