XML 75 R51.htm IDEA: XBRL DOCUMENT
v3.22.4

Summary of Significant Accounting Policies - Narrative (Details) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2022 USD ($) numberOfReportingUnit plant segment | Dec. 31, 2021 USD ($) | Dec. 31, 2020 USD ($)
Property, Plant and Equipment [Line Items] |  |  |
Number of operating segments | segment | 3 |  |
Number of jointly owned electric generation plants | plant | 2 |  |
Number of jointly owned major transmission lines | plant | 5 |  |
Number of reporting units | numberOfReportingUnit | 3 |  |
Electric Plant in Service |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Interest costs capitalized | $ | $ 0.9 | $ 0.6 | $ 2.1
OTP | Coyote Creek Mining Company, L.L.C. (CCMC) | Lignite Sales Agreement |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Variable interest entity, reporting entity involvement, maximum loss exposure, amount | $ | $ 45.0 |  |
Variable interest entity, reporting entity involvement, maximum loss exposure (as a percent) | 35.00% |  |
Minimum |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Intangible asset, useful life | 15 years |  |
Operating lease, term | 1 year |  |
Maximum |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Intangible asset, useful life | 20 years |  |
Operating lease, term | 10 years |  |

X
- Definition Number of Jointly Owned Electric Generation Plants + References No definition available. + Details
Name: | ottr_NumberOfJointlyOwnedElectricGenerationPlants
Namespace Prefix: | ottr_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of Jointly Owned Major Transmission Lines + References No definition available. + Details
Name: | ottr_NumberOfJointlyOwnedMajorTransmissionLines
Namespace Prefix: | ottr_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage of the reporting entity's maximum amount of exposure to loss as a result of its involvement with the Variable Interest Entity (VIE). + References No definition available. + Details
Name: | ottr_VariableInterestEntityReportingEntityInvolvementMaximumLossExposurePercentage
Namespace Prefix: | ottr_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Useful life of finite-lived intangible assets, 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_FiniteLivedIntangibleAssetUsefulLife
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of interest capitalized during the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b) -URI https://asc.fasb.org/extlink&oid=6450988&loc=d3e26243-108391 + Details
Name: | us-gaap_InterestCostsCapitalized
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Term of lessee's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a)(3) -URI https://asc.fasb.org/extlink&oid=128292326&loc=SL77918673-209980 + Details
Name: | us-gaap_LesseeOperatingLeaseTermOfContract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 18 -URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8672-108599 + Details
Name: | us-gaap_NumberOfOperatingSegments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of reporting units tested for impairment of goodwill. A reporting unit is an operating segment or one level below an operating segment. + References No definition available. + Details
Name: | us-gaap_NumberOfReportingUnits
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_PropertyPlantAndEquipmentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The reporting entity's maximum amount of exposure to loss as a result of its involvement with the Variable Interest Entity (VIE). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (c) -URI https://asc.fasb.org/extlink&oid=123419778&loc=d3e5747-111685 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph b -URI https://asc.fasb.org/extlink&oid=123419778&loc=d3e5728-111685 + Details
Name: | us-gaap_VariableInterestEntityEntityMaximumLossExposureAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_PublicUtilityAxis=ottr_ElectricPlantMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=ottr_OtterTailPowerCompanyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ConsolidatedEntitiesAxis=ottr_CoyoteCreekMiningCompanyLLCCCMCMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_TypeOfArrangementAxis=ottr_LigniteSalesAgreementMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |