Nameplate Capacity

No definition available.

Name:	nix_NameplateCapacity
Namespace Prefix:	nix_
Data Type:	dtr-types1:powerItemType
Balance Type:	na
Period Type:	instant

- Definition

Rest Debt Interest Rate

+ References

No definition available.

+ Details

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Namespace Prefix:	nix_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- 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.

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+ Details

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Period Type:	duration

- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The cash inflow from additional borrowings, net of cash paid to third parties in connection with debt origination.

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Namespace Prefix:	us-gaap_
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Balance Type:	debit
Period Type:	duration

- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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

- Details

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

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_JuniorNotesMember
Namespace Prefix:
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Balance Type:
Period Type:

Long-Term Debt (Narrative) (Details) $ in Millions	Sep. 09, 2024 USD ($)	Jun. 24, 2024 USD ($)	May 16, 2024 USD ($)	Mar. 14, 2024 USD ($)	Sep. 30, 2024 MW	Dec. 31, 2023
Debt Instrument [Line Items]
Second TCA Debt Interest Rate						6.50%
Rosewater
Debt Instrument [Line Items]
Nameplate Capacity \| MW					102
Senior Notes \| NiSource
Debt Instrument [Line Items]
Senior Notes		$ 600.0		$ 650.0
Debt, Weighted Average Interest Rate		5.20%		5.35%
Proceeds from Debt, Net of Issuance Costs		$ 593.7		$ 642.6
Junior Notes \| NiSource
Debt Instrument [Line Items]
Senior Notes	$ 500.0		$ 500.0
Debt, Weighted Average Interest Rate	6.375%		6.95%
Proceeds from Debt, Net of Issuance Costs	$ 493.6		$ 493.4
Second TCA Debt Interest Rate	2.527%		2.451%