Long-Term Debt (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2016	Mar. 15, 2016
Debt Instrument [Line Items]
Swap Forecasted Debt Issuance	2018
Nisource Finance
Debt Instrument [Line Items]
Subsidiary Ownership Percent	100.00%
Nisource Finance \| Interest Rate Swap
Debt Instrument [Line Items]
Notional Amount of Forward-Starting Interest rate Swap Agreements	$ 500.0
Loss on Fair Value Hedge Ineffectiveness	0.0
Nisource Finance \| Variable Rate Term Loan Due 2019
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 500.0
Debt Instrument, Maturity Date	Mar. 29, 2019
Amount of debt outstanding	$ 500.0
Nisource Finance \| Senior Notes
Debt Instrument [Line Items]
Debt Instrument, Repurchase Amount		$ 201.5
Debt Instrument, Interest Rate, Stated Percentage		10.75%

Notional Amount of Forward-Starting Interest rate Swap Agreements

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- Definition

Subsidiary Ownership Percentage

+ References

No definition available.

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- Definition

Swap Forecasted Debt Issuance

+ References

No definition available.

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- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

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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))
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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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- Definition

Fair value amount of debt instrument that was repurchased.

+ References

No definition available.

+ Details

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- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 210
-Section S99
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-Subparagraph (SX 210.7-03(a)(16))
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- Definition

Amount of recognized loss from the hedging ineffectiveness of a fair value hedge.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 25
-Section 50
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- Details

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