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Gas in Storage (Narrative) (Details) - USD ($) $ in Millions | Jun. 30, 2023 | Dec. 31, 2022
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Gas in Storage [Abstract] |  |
LIFO Inventory Amount | $ 11.6 | $ 0.0

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- Definition Gas in Storage [Abstract] + References No definition available. + Details
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Namespace Prefix: | nix_
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Balance Type: | na
Period Type: | duration

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- Definition The amount of LIFO (last in first out) inventory present at the reporting date when inventory is also valued using different valuation methods. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org//1943274/2147483489/210-10-50-1 + Details
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Namespace Prefix: | us-gaap_
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Balance Type: | debit
Period Type: | instant