XML 63 R52.htm IDEA: XBRL DOCUMENT
v3.25.3

Regulatory Matters - Narrative (Details) - USD ($) $ in Millions | Oct. 31, 2025 | Jun. 04, 2025
--- | --- | ---
South Dakota Rate Case | SDPUC |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Requested rate increase, amount |  | $ 5.7
Requested rate increase, percent (as a percent) |  | 12.50%
Requested return on base rate, percent (as a percent) |  | 8.29%
Requested return on equity, percent (as a percent) |  | 10.80%
Requested equity ratio, percent (as a percent) |  | 53.54%
Requested rate increase rates on interim, term |  | 180 days
Minnesota Rate Case | MPUC | Subsequent Event |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Requested rate increase, amount | $ 44.8 |
Requested rate increase, percent (as a percent) | 17.70% |
Requested return on base rate, percent (as a percent) | 7.92% |
Requested return on equity, percent (as a percent) | 10.65% |
Requested equity ratio, percent (as a percent) | 53.50% |
Requested accelerated recovery of remaining investments | $ 4.3 |
Requested interim rate , increase amount | $ 31.8 |
Requested interim rate increase percentage (as a percent) | 12.60% |

X
- Definition Public Utilities, Requested Accelerated Recovery Of Remaining Investments + References No definition available. + Details
Name: | ottr_PublicUtilitiesRequestedAcceleratedRecoveryOfRemainingInvestments
Namespace Prefix: | ottr_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Public Utilities, Requested Equity Ratio, Percentage + References No definition available. + Details
Name: | ottr_PublicUtilitiesRequestedEquityRatioPercentage
Namespace Prefix: | ottr_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Public Utilities, Requested Rate Increase, Maximum Term + References No definition available. + Details
Name: | ottr_PublicUtilitiesRequestedRateIncreaseMaximumTerm
Namespace Prefix: | ottr_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Public Utilities, Requested Return On Rate Base, Percentage + References No definition available. + Details
Name: | ottr_PublicUtilitiesRequestedReturnOnRateBasePercentage
Namespace Prefix: | ottr_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Schedule of Regulatory Assets and Liabilities + References No definition available. + Details
Name: | ottr_ScheduleOfRegulatoryAssetsAndLiabilitiesLineItems
Namespace Prefix: | ottr_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of public utility's interim rate increase (decrease) allowed while waiting final decision of regulatory agency. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesInterimRateIncreaseDecreaseAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Percentage of public utility's interim rate increase (decrease) allowed while waiting final decision of regulatory agency. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesInterimRateIncreaseDecreasePercentage
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of public utility's requested rate increase (decrease) with regulatory agency. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesRequestedRateIncreaseDecreaseAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Percentage of public utility's requested rate increase (decrease) with regulatory agency. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesRequestedRateIncreaseDecreasePercentage
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of public utility's requested return on equity. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesRequestedReturnOnEquityPercentage
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=ottr_SouthDakotaRateCaseMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAgencyAxis=ottr_SDPUCMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=ottr_MinnesotaRateCaseMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAgencyAxis=ottr_MPUCMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |