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Long-Term Debt (Narrative) (Details) - USD ($) $ in Millions | 3 Months Ended |  |
--- | --- | --- | ---
Mar. 31, 2017 | Apr. 03, 2017 | Mar. 27, 2017
Nisource Finance |  |  |
Debt Instrument [Line Items] |  |  |
Subsidiary Ownership Percent | 100.00% |  |
Medium Term Note Redeemed 2017 Note 1 | Nisource Capital Markets Inc | Medium-term Notes |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Repurchased Face Amount |  |  | $ 30.0
Debt Instrument, Interest Rate, Stated Percentage |  |  | 7.86%
Medium Term Note Redeemed 2017 Note 2 | Nisource Capital Markets Inc | Medium-term Notes |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Repurchased Face Amount |  |  | $ 2.0
Debt Instrument, Interest Rate, Stated Percentage |  |  | 7.85%
Medium Term Note Redeemed 2017 Note 3 | Subsequent Event | Nisource Capital Markets Inc | Medium-term Notes |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Repurchased Face Amount |  | $ 12.0 |
Debt Instrument, Interest Rate, Stated Percentage |  | 7.82% |
Medium Term Note Redeemed 2017 Note 4 | Subsequent Event | Nisource Capital Markets Inc | Medium-term Notes |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Repurchased Face Amount |  | $ 10.0 |
Debt Instrument, Interest Rate, Stated Percentage |  | 7.92% |
Medium Term Note Redeemed 2017 Note 5 | Subsequent Event | Nisource Capital Markets Inc | Medium-term Notes |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Repurchased Face Amount |  | $ 2.0 |
Debt Instrument, Interest Rate, Stated Percentage |  | 7.93% |
Medium Term Note Redeemed 2017 Note 6 | Subsequent Event | Nisource Capital Markets Inc | Medium-term Notes |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Repurchased Face Amount |  | $ 1.0 |
Debt Instrument, Interest Rate, Stated Percentage |  | 7.94% |

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- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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