XML 101 R78.htm IDEA: XBRL DOCUMENT
v3.20.2

Long-Term Debt (Narrative) (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended |  |  |
--- | --- | --- | --- | --- | ---
Sep. 30, 2020 | Sep. 30, 2019 | Sep. 30, 2020 | Sep. 30, 2019 | Aug. 31, 2020 | Aug. 18, 2020 | Apr. 13, 2020
Debt Instrument [Line Items] |  |  |  |  |  |  |
Debt Instrument Tendered |  |  | $ 969.3 |  |  |  |
Gain (Loss) on Extinguishment of Debt | $ (243.4) | $ 0.0 | (243.4) | $ 0.0 |  |  |
Working Capital Adjustment | $ 5.3 |  | $ 5.3 |  |  |  |
3.60% Notes Due 2030 [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 3.60% |  | 3.60% |  |  |  |
0.95% Notes Due 2025 [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Debt Instrument, Interest Rate, Stated Percentage |  |  |  |  |  | 0.95% |
1.70% Notes Due 2031 [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Debt Instrument, Interest Rate, Stated Percentage |  |  |  |  |  | 1.70% |
4.45% Notes Due 2021 [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 4.45% |  | 4.45% |  | 4.45% |  |
2.65% Notes Due 2022 [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 2.65% |  | 2.65% |  | 2.65% |  |
3.85% Notes Due 2023 [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 3.85% |  | 3.85% |  | 3.85% |  |
3.65% Notes Due 2023 [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 3.65% |  | 3.65% |  | 3.65% |  |
6.25% Notes Due 2040 [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Debt Instrument, Interest Rate, Stated Percentage |  |  |  |  | 6.25% |  |
5.95% Notes Due 2041 [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Debt Instrument, Interest Rate, Stated Percentage |  |  |  |  | 5.95% |  |
Senior Note Redeemed August & September 2020 [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Debt Instrument, Repurchased Face Amount | $ 609.3 |  | $ 609.3 |  |  |  |
Gain (Loss) on Extinguishment of Debt | $ 231.7 |  |  |  |  |  |
5.89% Notes Due 2025 [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 5.89% |  | 5.89% |  |  |  |
Note Redeemed September 2020 [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Debt Instrument, Repurchased Face Amount | $ 25.0 |  | $ 25.0 |  |  |  |
Gain (Loss) on Extinguishment of Debt | $ 11.7 |  |  |  |  |  |
6.26% Notes Due 2028 [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Debt Instrument, Interest Rate, Stated Percentage |  |  |  |  | 6.26% |  |
Senior Notes |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  |  |  | $ 1,000.0
Senior Notes | 3.60% Notes Due 2030 [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Proceeds from Debt, Net of Issuance Costs |  |  | 987.8 |  |  |  |
Senior Notes | 0.95% Notes Due 2025 [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  |  | $ 1,250.0 |
Senior Notes | 1.70% Notes Due 2031 [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  |  | $ 750.0 |
Senior Notes | 0.95% Notes Due 2025 and 1.70% Notes Due 2031 [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Proceeds from Debt, Net of Issuance Costs |  |  | $ 1,980.4 |  |  |  |

X
- Definition Debt Instrument Tendered + References No definition available. + Details
Name: | nix_DebtInstrumentTendered
Namespace Prefix: | nix_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Working Capital Adjustment + References No definition available. + Details
Name: | nix_WorkingCapitalAdjustment
Namespace Prefix: | nix_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Face (par) amount of debt instrument at time of issuance. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28551-108399 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400 + Details
Name: | us-gaap_DebtInstrumentFaceAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -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=120391452&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
- Definition Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 50 -Section 40 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=117329964&loc=d3e12355-112629 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 50 -Section 40 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=117329964&loc=d3e12317-112629 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585 + Details
Name: | us-gaap_GainsLossesOnExtinguishmentOfDebt
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The cash inflow from additional borrowings, net of cash paid to third parties in connection with debt origination. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3255-108585 + Details
Name: | us-gaap_ProceedsFromDebtNetOfIssuanceCosts
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_DebtInstrumentAxis=nix_A3.60NotesDue2030Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=nix_A095NotesDue2025Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=nix_A170NotesDue2031Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=nix_A445NotesDue2021Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=nix_A265NotesDue2022Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=nix_A385NotesDue2023Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=nix_A365NotesDue2023Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=nix_A625NotesDue2040Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=nix_A595NotesDue2041Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=nix_SeniorNoteRedeemedAugustSeptember2020Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=nix_A589NotesDue2025Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=nix_NoteRedeemedSeptember2020Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=nix_A626NotesDue2028Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

X
- Details
Name: | us-gaap_DebtInstrumentAxis=nix_A095NotesDue2025And170NotesDue2031Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |