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Income Taxes - Narrative (Details) | 12 Months Ended
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Dec. 31, 2022
Income Tax Disclosure [Abstract] |
Period for unrecognized tax benefits not expected change | 12 months

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- Definition Represents the period over which there is no significant expected change in the unrecognized tax benefits. + References No definition available. + Details
Name: | ottr_PeriodForUnrecognizedTaxBenefitsNotExpectedChange
Namespace Prefix: | ottr_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- References No definition available. + Details
Name: | us-gaap_IncomeTaxDisclosureAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration