XML 44 R79.htm IDEA: XBRL DOCUMENT
v3.20.1

Other Commitments And Contingencies Other Commitments and Contingencies (Expense and Insurance Recoveries) (Details) - USD ($) $ in Millions | 3 Months Ended | 4 Months Ended | 16 Months Ended | 19 Months Ended
--- | --- | --- | --- | ---
Mar. 31, 2020 | Dec. 31, 2018 | Dec. 31, 2019 | Mar. 31, 2020
Expense and Insurance Recoveries [Line Items] |  |  |  |
Third-party claims | $ 0 |  | $ 1,041 | $ 1,041
Other incident-related costs | 9 |  | 420 | 429
Total | 9 | $ 1,023 | 1,461 | 1,470
Insurance recoveries recorded | 0 |  | (800) | (800)
Total costs incurred | $ 9 |  | $ 661 | $ 670

X
- Definition Costs Resulting from the Greater Lawrence Incident + References No definition available. + Details
Name: | nix_CostsResultingfromtheGreaterLawrenceIncident
Namespace Prefix: | nix_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition [Line Items] for Expense and Insurance Recoveries [Table] + References No definition available. + Details
Name: | nix_ExpenseandInsuranceRecoveriesLineItems
Namespace Prefix: | nix_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Expenses other than third party claims + References No definition available. + Details
Name: | nix_ExpensesOtherThanThirdPartyClaims
Namespace Prefix: | nix_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Expenses Related to Third-Party Claims + References No definition available. + Details
Name: | nix_ExpensesRelatedtoThirdPartyClaims
Namespace Prefix: | nix_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Greater Lawrence Incident Impact on Operation and Maintenance Expense + References No definition available. + Details
Name: | nix_GreaterLawrenceIncidentImpactonOperationandMaintenanceExpense
Namespace Prefix: | nix_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The amount recovered from insurance. These recoveries reduce costs and losses that are reported as a separate line item under operating expenses. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.3) -URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227 + Details
Name: | us-gaap_InsuranceRecoveries
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration