XML 68 R57.htm IDEA: XBRL DOCUMENT
v3.21.2

Risk Management Activities (Schedule of Derivative Instruments in Statement of Financial Position, Fair Value) (Details) - USD ($) $ in Millions | Sep. 30, 2021 | Dec. 31, 2020
--- | --- | ---
Risk Management Assets Current |  |
Derivatives, Fair Value [Line Items] |  |
Risk management assets | $ 27.9 | $ 10.4
Risk Management Assets Noncurrent |  |
Derivatives, Fair Value [Line Items] |  |
Risk management assets | 18.8 | 2.8
Risk Management Liabilities Current |  |
Derivatives, Fair Value [Line Items] |  |
Risk management liabilities | 47.0 | 78.2
Risk Management Liabilities Noncurrent |  |
Derivatives, Fair Value [Line Items] |  |
Risk management liabilities | 75.7 | 144.6
Interest Rate Risk | Risk Management Assets Current |  |
Derivatives, Fair Value [Line Items] |  |
Risk management assets | 0.0 | 0.0
Interest Rate Risk | Risk Management Assets Noncurrent |  |
Derivatives, Fair Value [Line Items] |  |
Risk management assets | 0.0 | 0.0
Interest Rate Risk | Risk Management Liabilities Current |  |
Derivatives, Fair Value [Line Items] |  |
Risk management liabilities | 46.6 | 70.9
Interest Rate Risk | Risk Management Liabilities Noncurrent |  |
Derivatives, Fair Value [Line Items] |  |
Risk management liabilities | 68.8 | 99.5
Commodity Price Risk Programs | Risk Management Assets Current |  |
Derivatives, Fair Value [Line Items] |  |
Risk management assets | 27.9 | 10.4
Commodity Price Risk Programs | Risk Management Assets Noncurrent |  |
Derivatives, Fair Value [Line Items] |  |
Risk management assets | 18.8 | 2.8
Commodity Price Risk Programs | Risk Management Liabilities Current |  |
Derivatives, Fair Value [Line Items] |  |
Risk management liabilities | 0.4 | 7.3
Commodity Price Risk Programs | Risk Management Liabilities Noncurrent |  |
Derivatives, Fair Value [Line Items] |  |
Risk management liabilities | $ 6.9 | $ 45.1

X
- Definition Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 22 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226052-175313 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=123594938&loc=d3e13433-108611 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 + Details
Name: | us-gaap_DerivativeAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=123594938&loc=d3e13433-108611 Reference 4: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 22 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226052-175313 + Details
Name: | us-gaap_DerivativeLiabilities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
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_DerivativesFairValueLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_BalanceSheetLocationAxis=nix_RiskManagementAssetsCurrentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BalanceSheetLocationAxis=nix_RiskManagementAssetsNoncurrentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BalanceSheetLocationAxis=nix_RiskManagementLiabilitiesCurrentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BalanceSheetLocationAxis=nix_RiskManagementLiabilitiesNoncurrentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateRiskMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=nix_CommodityPriceRiskProgramsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |