XML 84 R60.htm IDEA: XBRL DOCUMENT
v3.22.4

Regulatory Matters - Regulatory Assets and Liabilities (Details) - USD ($) $ in Thousands |  |  | 6 Months Ended | 12 Months Ended
--- | --- | --- | --- | ---
Feb. 01, 2022 | Dec. 03, 2020 | Dec. 31, 2022 | Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020
Schedule of Regulatory Assets and Liabilities [Line Items] |  |  |  |  |  |
Regulatory assets - current |  |  | $ 24,999 | $ 24,999 | $ 27,342 |
Regulatory assets, long-term |  |  | 94,655 | 94,655 | 125,508 |
Regulatory liabilities, current |  |  | 17,300 | 17,300 | 24,844 |
Regulatory liabilities, long -term |  |  | 244,497 | 244,497 | 234,430 |
Reduction of regulatory assets |  |  |  | (2,464) | (4,803) | $ (4,070)
Minnesota Rate Case | MPUC |  |  |  |  |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |  |  |  |  |
Revenue, approved rate increase, amount |  | $ 6,900 | 15,300 | 4,100 |  |
Revenue, approved rate increase, percent |  | 3.20% |  |  |  |
Revenue requirement amount | $ 209,000 |  |  |  |  |
Approved return on base rate, percent | 7.18% |  |  |  |  |
Approved return on equity, percent | 9.48% |  |  |  |  |
Approved equity ratio, percent | 52.50% |  |  |  |  |
Recovery period | 5 years |  |  |  |  |
Approved cap of annual base revenues, percent | 4.00% |  |  |  |  |
Excess capacity auction revenue |  |  |  | 5,300 |  |
Reduction of regulatory assets |  |  |  | 2,600 |  |
Refund liability |  |  |  | 1,800 |  |
Deferred Income Taxes |  |  |  |  |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |  |  |  |  |
Regulatory liabilities, current |  |  | 0 | 0 | 0 |
Regulatory liabilities, long -term |  |  | 131,480 | 131,480 | 129,437 |
Plant Removal Obligations |  |  |  |  |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |  |  |  |  |
Regulatory liabilities, current |  |  | 8,509 | 8,509 | 8,306 |
Regulatory liabilities, long -term |  |  | 105,733 | 105,733 | 101,595 |
Fuel Clause Adjustments |  |  |  |  |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |  |  |  |  |
Regulatory liabilities, current |  |  | 365 | 365 | 1,554 |
Regulatory liabilities, long -term |  |  | 0 | $ 0 | 0 |
Regulatory liabilities - remaining recovery/refund period |  |  |  | 1 year |  |
Alternative Revenue Program Riders |  |  |  |  |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |  |  |  |  |
Regulatory liabilities, current |  |  | 2,504 | $ 2,504 | 5,772 |
Regulatory liabilities, long -term |  |  | 7,136 | 7,136 | 3,336 |
Pension and Other Postretirement Benefit Plans |  |  |  |  |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |  |  |  |  |
Regulatory liabilities, current |  |  | 5,589 | 5,589 | 2,603 |
Regulatory liabilities, long -term |  |  | 0 | $ 0 | 0 |
Regulatory liabilities - remaining recovery/refund period |  |  |  | 1 year |  |
Derivative Instruments |  |  |  |  |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |  |  |  |  |
Regulatory liabilities, current |  |  | 0 | $ 0 | 6,214 |
Regulatory liabilities, long -term |  |  | 0 | $ 0 | 0 |
Regulatory liabilities - remaining recovery/refund period |  |  |  | 1 year |  |
Other |  |  |  |  |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |  |  |  |  |
Regulatory liabilities, current |  |  | 333 | $ 333 | 395 |
Regulatory liabilities, long -term |  |  | 148 | 148 | 62 |
Pension and Other Postretirement Benefit Plans |  |  |  |  |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |  |  |  |  |
Regulatory assets - current |  |  | 0 | 0 | 7,791 |
Regulatory assets, long-term |  |  | 88,354 | 88,354 | 114,961 |
Alternative Revenue Program Riders |  |  |  |  |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |  |  |  |  |
Regulatory assets - current |  |  | 5,679 | 5,679 | 11,889 |
Regulatory assets, long-term |  |  | 2,508 | $ 2,508 | 5,564 |
Regulatory assets - Remaining recovery/refund period |  |  |  | 2 years |  |
Asset Retirement Obligations |  |  |  |  |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |  |  |  |  |
Regulatory assets - current |  |  | 0 | $ 0 | 0 |
Regulatory assets, long-term |  |  | 1,467 | 1,467 | 742 |
ISO Cost Recovery Trackers |  |  |  |  |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |  |  |  |  |
Regulatory assets - current |  |  | 575 | 575 | 0 |
Regulatory assets, long-term |  |  | 314 | $ 314 | 1,342 |
Regulatory assets - Remaining recovery/refund period |  |  |  | 2 years |  |
Unrecovered Project Costs |  |  |  |  |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |  |  |  |  |
Regulatory assets - current |  |  | 320 | $ 320 | 2,136 |
Regulatory assets, long-term |  |  | 990 | $ 990 | 1,455 |
Regulatory assets - Remaining recovery/refund period |  |  |  | 5 years |  |
Deferred Rate Case Expenses |  |  |  |  |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |  |  |  |  |
Regulatory assets - current |  |  | 377 | $ 377 | 607 |
Regulatory assets, long-term |  |  | 754 | $ 754 | 1,131 |
Regulatory assets - Remaining recovery/refund period |  |  |  | 2 years |  |
Debt Reacquisition Premiums |  |  |  |  |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |  |  |  |  |
Regulatory assets - current |  |  | 25 | $ 25 | 100 |
Regulatory assets, long-term |  |  | 216 | $ 216 | 240 |
Regulatory assets - Remaining recovery/refund period |  |  |  | 10 years |  |
Fuel Clause Adjustments |  |  |  |  |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |  |  |  |  |
Regulatory assets - current |  |  | 10,893 | $ 10,893 | 4,819 |
Regulatory assets, long-term |  |  | 0 | $ 0 | 0 |
Regulatory assets - Remaining recovery/refund period |  |  |  | 1 year |  |
Derivative Instruments |  |  |  |  |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |  |  |  |  |
Regulatory assets - current |  |  | 7,130 | $ 7,130 | 0 |
Regulatory assets, long-term |  |  | 0 | $ 0 | 0 |
Regulatory assets - Remaining recovery/refund period |  |  |  | 1 year |  |
Other |  |  |  |  |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |  |  |  |  |
Regulatory assets - current |  |  | 0 | $ 0 | 0 |
Regulatory assets, long-term |  |  | $ 52 | $ 52 | $ 73 |

X
- Definition Excess Capacity Auction Revenue + References No definition available. + Details
Name: | ottr_ExcessCapacityAuctionRevenue
Namespace Prefix: | ottr_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Public Utilities, Approved Cap Of Annual Base Revenues, Percentage + References No definition available. + Details
Name: | ottr_PublicUtilitiesApprovedCapOfAnnualBaseRevenuesPercentage
Namespace Prefix: | ottr_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

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

X
- Definition Public Utilities, Approved Recovery Period Of Asset + References No definition available. + Details
Name: | ottr_PublicUtilitiesApprovedRecoveryPeriodOfAsset
Namespace Prefix: | ottr_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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

X
- Definition Public Utilities, Refund Liability + References No definition available. + Details
Name: | ottr_PublicUtilitiesRefundLiability
Namespace Prefix: | ottr_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Public Utilities, Revenue Requirement + References No definition available. + Details
Name: | ottr_PublicUtilitiesRevenueRequirement
Namespace Prefix: | ottr_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
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 The increase (decrease) during the reporting period in the value of other assets that are created when regulatory agencies permits public utilities to defer costs to the balance sheet. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3602-108585 + Details
Name: | us-gaap_IncreaseDecreaseInOtherRegulatoryAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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

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

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

X
- Definition Amortization period for the recovery of regulatory asset, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | us-gaap_RegulatoryAssetAmortizationPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are expected to be recovered through revenue sources within one year or the normal operating cycle, if longer. Such costs are capitalized if they meet both of the following criteria: a. It is probable that future revenue in an amount at least equal to the capitalized cost will result from inclusion of that cost in allowable costs for rate-making purposes. b. Based on available evidence, the future revenue will be provided to permit recovery of the previously incurred cost rather than to provide for expected levels of similar future costs. If the revenue will be provided through an automatic rate-adjustment clause, this criterion requires that the regulator's intent clearly be to permit recovery of the previously incurred cost. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 1 -URI https://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382 + Details
Name: | us-gaap_RegulatoryAssetsCurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are not expected to be recovered through revenue sources within one year or the normal operating cycle if longer. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 1 -URI https://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382 + Details
Name: | us-gaap_RegulatoryAssetsNoncurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amortization period for the recovery of regulatory liability, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | us-gaap_RegulatoryLiabilityAmortizationPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount for the individual regulatory current liability as itemized in a table of regulatory current liabilities as of the end of the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 405 -Section 25 -Paragraph 1 -URI https://asc.fasb.org/extlink&oid=6500807&loc=d3e48068-110394 + Details
Name: | us-gaap_RegulatoryLiabilityCurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The amount for the individual regulatory noncurrent liability as itemized in a table of regulatory noncurrent liabilities as of the end of the period. + 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 210.5-02.24) -URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_RegulatoryLiabilityNoncurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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_RegulatoryLiabilityAxis=ottr_DeferredIncomeTaxesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=ottr_PlantRemovalObligationsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=ottr_FuelClauseAdjustmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=ottr_AlternativeRevenueProgramRidersMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=ottr_PensionAndOtherPostretirementBenefitPlansMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=ottr_DerivativeLiabilitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=ottr_OtherRegulatoryLiabilitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=ottr_PensionAndOtherPostretirementBenefitPlansMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=ottr_AlternativeRevenueProgramRidersMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=ottr_AssetRetirementObligationsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=ottr_ISOCostRecoveryTrackersMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=ottr_UnrecoveredProjectCostsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=ottr_DeferredRateCaseExpensesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=ottr_DebtReacquisitionPremiumsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=ottr_FuelClauseAdjustmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=ottr_RegulatoryAssetDerivativeInstrumentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=ottr_OtherRegulatoryAssetsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |