XML 69 R58.htm IDEA: XBRL DOCUMENT
v3.21.2

Property, Plant, and Equipment (Narrative) (Details) $ in Millions | 6 Months Ended
--- | ---
Jun. 30, 2021 USD ($)
Property, Plant and Equipment [Line Items] |
Charges associated with Schahfer Generating Station Retirement | $ 8.6
Plant and Equipment associated with Schahfer Generating Station Retirement | $ 823.1

X
- Definition Charges associated with Schahfer Generating Station Retirement + References No definition available. + Details
Name: | nix_ChargesAssociatedWithSchahferGeneratingStationRetirement
Namespace Prefix: | nix_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Plant and Equipment Associated with Schahfer Generating Station Retirement + References No definition available. + Details
Name: | nix_PlantAndEquipmentAssociatedWithSchahferGeneratingStationRetirement
Namespace Prefix: | nix_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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_PropertyPlantAndEquipmentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration