XML 65 R54.htm IDEA: XBRL DOCUMENT v3.7.0.1

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%

X

- Definition

Subsidiary Ownership Percentage

+ References

No definition available.

+ Details

Name:	ni_SubsidiaryOwnershipPercentage
Namespace Prefix:	ni_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- 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

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

X

- 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.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Face (par) amount of the original debt instrument that was repurchased.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentRepurchasedFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Details

Name:	dei_LegalEntityAxis=ni_NisourceFinanceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DebtInstrumentAxis=ni_MediumTermNoteRedeemed2017Note1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	dei_LegalEntityAxis=ni_NisourceCapitalMarketsIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_MediumTermNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DebtInstrumentAxis=ni_MediumTermNoteRedeemed2017Note2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DebtInstrumentAxis=ni_MediumTermNoteRedeemed2017Note3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DebtInstrumentAxis=ni_MediumTermNoteRedeemed2017Note4Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DebtInstrumentAxis=ni_MediumTermNoteRedeemed2017Note5Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DebtInstrumentAxis=ni_MediumTermNoteRedeemed2017Note6Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: