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Income Taxes - Narrative (Details)	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Period for unrecognized tax benefits not expected change	12 months

X

- 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

X

- References

No definition available.

+ Details

Name:	us-gaap_IncomeTaxDisclosureAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration