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Other Commitments and Contingencies (Narrative) (Details) (USD $)
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6 Months Ended | 3 Months Ended | 3 Months Ended | 6 Months Ended | 108 Months Ended | 6 Months Ended | 108 Months Ended | 3 Months Ended | 6 Months Ended | 6 Months Ended | 12 Months Ended | 0 Months Ended | 6 Months Ended | ||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
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Jun. 30, 2011
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Jun. 30, 2009
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Jun. 21, 2011
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Dec. 31, 2010
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Jun. 21, 2010
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Jun. 30, 2008
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Sep. 16, 2005
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Jun. 30, 2011
Nisource Finance [Member]
Letters of Credit [Member]
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Jun. 30, 2011
Letters of Credit [Member]
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Dec. 31, 2010
Letters of Credit [Member]
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Jun. 30, 2011
Letters of Credit [Member]
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Mar. 31, 2011
Nisource Finance [Member]
Four-Year Revolving Credit Facility [Member]
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Mar. 03, 2011
Nisource Finance [Member]
Four-Year Revolving Credit Facility [Member]
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Jun. 30, 2011
Four-Year Revolving Credit Facility [Member]
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Dec. 31, 2010
Four-Year Revolving Credit Facility [Member]
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Mar. 31, 2011
Nisource Finance [Member]
Five-Year Credit Facility [Member]
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Jun. 30, 2011
Nisource Finance [Member]
Five-Year Credit Facility [Member]
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Jun. 30, 2011
Maximum [Member]
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Dec. 31, 2018
Maximum [Member]
Northern Indiana [Member]
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Jun. 30, 2011
Minimum [Member]
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Dec. 31, 2018
Minimum [Member]
Northern Indiana [Member]
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Jun. 30, 2011
Guarantees of Subsidiaries Debt [Member]
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Jun. 30, 2011
Nisource Finance [Member]
Guarantees Supporting Commodity Transactions of Subsidiaries [Member]
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Jun. 30, 2011
Guarantees Supporting Commodity Transactions of Subsidiaries [Member]
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Jun. 30, 2011
Other Guarantees [Member]
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Jun. 30, 2011
Nisource Finance [Member]
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Jun. 30, 2011
Nisource Finance [Member]
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Jun. 30, 2011
Whiting Clean Energy [Member]
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Jun. 30, 2008
Whiting Clean Energy [Member]
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Jun. 30, 2011
Millennium [Member]
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Jun. 30, 2011
Millennium [Member]
5.33% due June 30, 2027 [Member]
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Jun. 30, 2011
Millennium [Member]
6.00% due June 30, 2032 [Member]
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Jun. 30, 2011
Columbia Transmission [Member]
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Dec. 31, 2007
Columbia Transmission [Member]
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Nov. 22, 2008
Columbia Natural Resources [Member]
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Jun. 30, 2011
Columbia Natural Resources [Member]
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Dec. 31, 2010
Columbia Natural Resources [Member]
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Jan. 13, 2009
Columbia Natural Resources [Member]
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Oct. 24, 2008
Columbia Natural Resources [Member]
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Jan. 27, 2007
Columbia Natural Resources [Member]
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Aug. 20, 2010
National Emission Standard for Hazardous Air Pollutants [Member]
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Jun. 30, 2011
Former Propane Operations [Member]
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Jun. 30, 2011
Former Petroleum Operations [Member]
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| Guaranteed payments of debt | $ 7,214,200,000 | $ 38,000,000 | $ 5,830,900,000 | $ 153,100,000 | $ 153,100,000 | $ 321,800,000 | $ 16,200,000 | ||||||||||||||||||||||||||||||||||||
| Guarantees | 7,214,200,000 | 38,000,000 | 5,830,900,000 | 153,100,000 | 153,100,000 | 321,800,000 | 16,200,000 | ||||||||||||||||||||||||||||||||||||
| Revolving credit facility, maximum | 1,500,000,000 | 1,500,000,000 | 1,500,000,000 | 500,000,000 | 500,000,000 | ||||||||||||||||||||||||||||||||||||||
| Termination date of credit facility | March 3, 2015 | July 2011 | March 2015 | March 3, 2015 | |||||||||||||||||||||||||||||||||||||||
| Letters of credit facility amount outstanding | 506,000,000 | 1,107,500,000 | 38,000,000 | 38,000,000 | 32,500,000 | 506,000,000 | 14,200,000 | 506,000,000 | 506,000,000 | 16,200,000 | |||||||||||||||||||||||||||||||||
| Commercial Paper | 180,500,000 | ||||||||||||||||||||||||||||||||||||||||||
| Accounts receivable securitization agreements outstanding | 183,900,000 | 275,000,000 | 183,900,000 | 275,000,000 | 183,900,000 | 183,900,000 | |||||||||||||||||||||||||||||||||||||
| Sale of Whiting Clean Energy to BPAE | 216,700,000 | ||||||||||||||||||||||||||||||||||||||||||
| Portion of working capital | 16,100,000 | ||||||||||||||||||||||||||||||||||||||||||
| Total executed purchase and sales agreement guarantees | 220,000,000 | ||||||||||||||||||||||||||||||||||||||||||
| Additional purchase and sales agreement guarantees | 0 | 30,000,000 | |||||||||||||||||||||||||||||||||||||||||
| Face amount of notes | 725,000,000 | 1,000,000,000 | |||||||||||||||||||||||||||||||||||||||||
| Debt instrument maturity date | Jun. 30, 2027 | Jun. 30, 2032 | |||||||||||||||||||||||||||||||||||||||||
| Percentage of interest in Millennium | 47.50% | 47.50% | |||||||||||||||||||||||||||||||||||||||||
| Fair value of guarantee obligations | 1,500,000 | ||||||||||||||||||||||||||||||||||||||||||
| Compensatory and punitive damages charged against defendants | 404,300,000 | ||||||||||||||||||||||||||||||||||||||||||
| Total settlement amount preliminarily approved by Trial Court | 380,000,000 | ||||||||||||||||||||||||||||||||||||||||||
| Company's share of settlement liability | 28,800,000 | 338,800,000 | |||||||||||||||||||||||||||||||||||||||||
| Escrow fund | 28,700,000 | ||||||||||||||||||||||||||||||||||||||||||
| Contribution to qualified settlement fund | 338,500,000 | 330,500,000 | 85,500,000 | ||||||||||||||||||||||||||||||||||||||||
| Letter of credit to secure unpaid portion of settlement | 28,800,000 | 338,800,000 | |||||||||||||||||||||||||||||||||||||||||
| Letter of credit to secure unpaid portion of settlement | 254,000,000 | ||||||||||||||||||||||||||||||||||||||||||
| Maximum settlement liability unpaid | 300,000 | ||||||||||||||||||||||||||||||||||||||||||
| Investments in environmental mitigation projects | 9,500,000 | ||||||||||||||||||||||||||||||||||||||||||
| Payments in environmental mitigation projects | 3,500,000 | ||||||||||||||||||||||||||||||||||||||||||
| Recorded reserves to cover environmental remediation at various sites | 79,400,000 | 79,800,000 | |||||||||||||||||||||||||||||||||||||||||
| Payments for capital improvements | 840,000,000 | 570,000,000 | |||||||||||||||||||||||||||||||||||||||||
| Minimum estimates cost of compliance | 20,000,000 | ||||||||||||||||||||||||||||||||||||||||||
| Maximum estimates cost of compliance | 25,000,000 | ||||||||||||||||||||||||||||||||||||||||||
| Number of waste disposal sites identified by program | 84 | ||||||||||||||||||||||||||||||||||||||||||
| Number of sites in which initial investigations conducted | 56 | ||||||||||||||||||||||||||||||||||||||||||
| Number of sites in which follow-up investigation activities completed or are in progress | 50 | ||||||||||||||||||||||||||||||||||||||||||
| Number of sites in which remedial measures implemented or completed | 37 | ||||||||||||||||||||||||||||||||||||||||||
| Number of facilities AOC covered under conduct characterization and remediation activities, approximately | 245 | 50 | |||||||||||||||||||||||||||||||||||||||||
| 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 | 1,000,000 | ||||||||||||||||||||||||||||||||||||||||||
| Payment of fine | 3,500,000 | ||||||||||||||||||||||||||||||||||||||||||
| Additional capital improvements associated with air pollutants rule | 90,000,000 | 0 | |||||||||||||||||||||||||||||||||||||||||
| Invest in environmental mitigation projects | $ 9,500,000 | ||||||||||||||||||||||||||||||||||||||||||
| Expected number of years for capital improvements related to coal combustion residuals | 5 Years | ||||||||||||||||||||||||||||||||||||||||||
| Number of sites associated with former operations | 4 | 10 | |||||||||||||||||||||||||||||||||||||||||
| Number of EPA rules District of Columbia Circuit vacated | two | ||||||||||||||||||||||||||||||||||||||||||