XML 55 R44.htm IDEA: XBRL DOCUMENT
v3.21.1

Short-Term and Long-Term Borrowings - Breakdown of Outstanding Long-term Debt (Details) - USD ($) $ in Thousands | Mar. 31, 2021 | Dec. 31, 2020
--- | --- | ---
Debt Instrument [Line Items] |  |
Long-term debt | $ 767,000 | $ 767,169
Current Maturities Net of Unamortized Debt Issuance Costs | 139,941 | 140,087
Unamortized Long-Term Debt Issuance Costs | 2,574 | 2,650
Total Long-Term Debt Net of Unamortized Debt Issuance Costs | $ 624,485 | 624,432
Guaranteed Senior Notes |  |
Debt Instrument [Line Items] |  |
Rate | 3.55% |
Long-term debt | $ 80,000 | 80,000
Series 2011A Senior Unsecured Notes |  |
Debt Instrument [Line Items] |  |
Rate | 4.63% |
Long-term debt | $ 140,000 | 140,000
Series 2007B Senior Unsecured Notes |  |
Debt Instrument [Line Items] |  |
Rate | 6.15% |
Long-term debt | $ 30,000 | 30,000
Series 2007C Senior Unsecured Notes |  |
Debt Instrument [Line Items] |  |
Rate | 6.37% |
Long-term debt | $ 42,000 | 42,000
Series 2013A Senior Unsecured Notes |  |
Debt Instrument [Line Items] |  |
Rate | 4.68% |
Long-term debt | $ 60,000 | 60,000
Series 2019A Senior Unsecured Notes |  |
Debt Instrument [Line Items] |  |
Rate | 3.07% |
Long-term debt | $ 10,000 | 10,000
Series 2020A Senior Unsecured Notes |  |
Debt Instrument [Line Items] |  |
Rate | 3.22% |
Long-term debt | $ 10,000 | 10,000
Series 2020B Senior Unsecured Notes |  |
Debt Instrument [Line Items] |  |
Rate | 3.22% |
Long-term debt | $ 40,000 | 40,000
Series 2007D Senior Unsecured Notes |  |
Debt Instrument [Line Items] |  |
Rate | 6.47% |
Long-term debt | $ 50,000 | 50,000
Series 2019B Senior Unsecured Notes |  |
Debt Instrument [Line Items] |  |
Rate | 3.52% |
Long-term debt | $ 26,000 | 26,000
Series 2020C Senior Unsecured Notes |  |
Debt Instrument [Line Items] |  |
Rate | 3.62% |
Long-term debt | $ 10,000 | 10,000
Series 2013B Senior Unsecured Notes |  |
Debt Instrument [Line Items] |  |
Rate | 5.47% |
Long-term debt | $ 90,000 | 90,000
Series 2018A Senior Unsecured Notes |  |
Debt Instrument [Line Items] |  |
Rate | 4.07% |
Long-term debt | $ 100,000 | 100,000
Series 2019C Senior Unsecured Notes |  |
Debt Instrument [Line Items] |  |
Rate | 3.82% |
Long-term debt | $ 64,000 | 64,000
Series 2020D Senior Unsecured Notes |  |
Debt Instrument [Line Items] |  |
Rate | 3.92% |
Long-term debt | $ 15,000 | 15,000
PACE Note |  |
Debt Instrument [Line Items] |  |
Rate | 2.54% |
Long-term debt | $ 0 | $ 169

X
- Definition Contractual interest rate for funds borrowed, under the debt agreement. + 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 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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_DebtInstrumentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount, after accumulated amortization, of debt discount. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28541-108399 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400 + Details
Name: | us-gaap_DebtInstrumentUnamortizedDiscount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=120520924&loc=SL6031897-161870 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(16)) -URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878 Reference 4: 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(22)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_LongTermDebt
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. + 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 210.5-02.19,20) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_LongTermDebtCurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. + 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 210.5-02.22) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_LongTermDebtNoncurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_DebtInstrumentAxis=ottr_The355GuaranteedSeniorNotesDueDecember152026Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=ottr_SeniorUnsecuredNotes463SeriesADueDecember12021Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=ottr_SeniorUnsecuredNotes615SeriesBDueAugust202022Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=ottr_SeniorUnsecuredNotes637SeriesCDueAugust202027Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=ottr_SeniorUnsecuredNotes468SeriesADueFebruary272029Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=ottr_SeniorUnsecuredNotes307SeriesADueOctober102029Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=ottr_SeniorUnsecuredNotes307SeriesADueFebruary252030Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=ottr_SeniorUnsecuredNotes322SeriesBDueAugust202030Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=ottr_SeniorUnsecuredNotes647SeriesDDueAugust202037Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=ottr_SeniorUnsecuredNotes352SeriesBDueOctober102039Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=ottr_SeniorUnsecuredNotes362SeriesCDueFebruary252040Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=ottr_SeniorUnsecuredNotes547SeriesBDueFebruary272044Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=ottr_SeniorUnsecuredNotes407SeriesADueFebruary72048Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=ottr_SeniorUnsecuredNotes382SeriesCDueOctober102049Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=ottr_SeniorUnsecuredNotes392SeriesDDueFebruary252050Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=ottr_PartnershipInAssistingCommunityExpansionPaceNote254DueMarch182021Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |