v2.4.0.8

Other Commitments And Contingencies (Narrative) (Details) (USD $) In Millions, unless otherwise specified | 6 Months Ended |  |  |  |  |  |  | 12 Months Ended |  |  |  | 0 Months Ended |  |
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Jun. 30, 2013 | Dec. 31, 2012 | Jun. 30, 2013 MGP Sites | Dec. 31, 2012 MGP Sites | Jun. 30, 2013 Millennium Pipeline Company, L.L.C [Member] | Jun. 30, 2013 Columbia Transmission [Member] | Dec. 31, 2012 Columbia Transmission [Member] | Jun. 30, 2013 Guarantees Of Subsidiaries Debt [Member] | Jun. 30, 2013 Guarantees Supporting Energy Commodity Transactions Of Subsidiaries [Member] | Jun. 30, 2013 Letters Of Credit [Member] | Jun. 30, 2013 Other Guarantees [Member] | Jun. 30, 2013 Commercial Paper [Member] | Jun. 30, 2013 Accounts Receivable Securitization [Member] | Dec. 31, 2013 Maximum [Member] Northern Indiana [Member] | Dec. 31, 2013 Minimum [Member] Northern Indiana [Member] | Jun. 30, 2013 Letters Of Credit [Member] | Dec. 31, 2012 Letters Of Credit [Member] | May 31, 2012 TerminationDateMay152017 [Member] | May 15, 2012 Revolving Credit Facility [Member] | Jun. 30, 2013 Revolving Credit Facility [Member] | May 31, 2012 Revolving Credit Facility [Member]
Other Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Guarantees | $ 7,720.2 |  |  |  | $ 16.2 |  |  | $ 7,135.5 | $ 37.0 | $ 38.6 | $ 131.4 | $ 117.6 | $ 260.1 |  |  |  |  |  |  |  |
Revolving credit facility, maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,500.0 |  |  | 1,500.0
Revolving Credit Facility Expiration Date |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | May 15, 2017 |  |
Line of Credit Facility, Amount Outstanding | 0 | 44.0 |  |  |  |  |  |  |  |  |  |  |  |  |  | 38.6 | 36.4 |  |  | 0 |
Commercial paper | 117.6 | 499.6 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Accounts receivable securitization facility borrowings | 260.1 | 233.3 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Additional purchase and sales agreement guarantees | 42.0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of interest in Millennium | 47.50% |  |  |  | 47.50% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fair value of guarantee obligations |  |  |  |  | 1.5 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (Loss) Related to Litigation Settlement | 17.5 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Recorded reserves to cover environmental remediation at various sites | 156.4 | 160.6 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Payments for capital improvements |  |  |  |  |  |  |  |  |  |  |  |  |  | 865 | 835 |  |  |  |  |  |
Remaining Payments for Capital Improvements |  |  |  |  |  |  |  |  |  |  |  |  |  | 415 | 385 |  |  |  |  |  |
Number of waste disposal sites identified by program |  |  | 67 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Original number of facilities AOC covered under conduct characterization and remediation activities, approximately |  |  |  |  |  | 245 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of liquid removal points AOC covered under conduct characterization and remediation activities |  |  |  |  |  | 13,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of mercury measurement stations AOC covered under conduct characterization and remediation activities |  |  |  |  |  | 2,200 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of storage well locations AOC covered under conduct characterization and remediation activities |  |  |  |  |  | 3,700 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proposed penalty of NOV asserts violations of Pennsylvania Clean Streams law and Pennsylvania Solid Waste Management act |  |  |  |  |  | 1 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Increased liability for estimated remediation costs |  |  |  |  |  |  | 25.6 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Liability for estimated remediation costs |  |  | 134.6 | 132.6 |  | 15.5 | 21.7 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Reasonably possible remediation costs variance from reserve |  |  | $ 25 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Remaining number of facilities AOC covered under conduct characterization and remediation activities, approximately |  |  |  |  |  | 50 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |

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