XML 54 R42.htm IDEA: XBRL DOCUMENT
v3.25.2

Reinsurance - Excess of Loss Reinsurance (Details) $ in Thousands |  |  |  |  |  |  |  |  |  | 6 Months Ended | 12 Months Ended
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Jun. 01, 2025 USD ($) | Mar. 01, 2025 USD ($) | Apr. 01, 2024 USD ($) | Oct. 23, 2023 USD ($) | Apr. 01, 2023 USD ($) | Apr. 26, 2022 USD ($) | Apr. 01, 2022 USD ($) | Aug. 03, 2021 USD ($) | Feb. 02, 2021 USD ($) | Jun. 30, 2025 USD ($) | Dec. 31, 2024 USD ($)
Eligible New Insurance Written In 2026 |  |  |  |  |  |  |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |  |  |  |  |  |  |
Excess of loss reinsurance coverage, initial and remaining |  |  |  |  |  |  |  |  |  | $ 184,000 |
2025 Traditional XOL |  |  |  |  |  |  |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |  |  |  |  |  |  |
Amortization period excess of loss reinsurance coverage | 10 years |  |  |  |  |  |  |  |  |  |
Excess of loss reinsurance coverage, initial and remaining | $ 160,000 |  |  |  |  |  |  |  |  |  |
2024 Traditional XOL |  |  |  |  |  |  |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |  |  |  |  |  |  |
Amortization period excess of loss reinsurance coverage |  |  | 10 years |  |  |  |  |  |  |  |
Initial First Layer Retention |  |  | $ 125,016 |  |  |  |  |  |  |  |
Remaining First Layer Retention |  |  |  |  |  |  |  |  |  | 124,948 | $ 125,016
Excess of loss reinsurance coverage, initial and remaining |  |  | $ 187,220 |  |  |  |  |  |  | 187,220 | 187,220
2023 Traditional XOL |  |  |  |  |  |  |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |  |  |  |  |  |  |
Amortization period excess of loss reinsurance coverage |  |  |  |  | 10 years |  |  |  |  |  |
Initial First Layer Retention |  |  |  |  | $ 70,578 |  |  |  |  |  |
Remaining First Layer Retention |  |  |  |  |  |  |  |  |  | 70,006 | 70,401
Excess of loss reinsurance coverage, initial and remaining |  |  |  |  | $ 96,942 |  |  |  |  | 79,196 | 91,404
2022 Traditional XOL |  |  |  |  |  |  |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |  |  |  |  |  |  |
Amortization period excess of loss reinsurance coverage |  |  |  |  |  |  | 10 years |  |  |  |
Initial First Layer Retention |  |  |  |  |  |  | $ 82,523 |  |  |  |
Remaining First Layer Retention |  |  |  |  |  |  |  |  |  | 79,712 | 81,112
Excess of loss reinsurance coverage, initial and remaining |  |  |  |  |  |  | $ 142,642 |  |  | 109,115 | 124,344
2020 Traditional XOL |  |  |  |  |  |  |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |  |  |  |  |  |  |
Amortization period excess of loss reinsurance coverage |  | 10 years |  |  |  |  |  |  |  |  |
Initial First Layer Retention |  | $ 68,343 |  |  |  |  |  |  |  |  |
Remaining First Layer Retention |  |  |  |  |  |  |  |  |  | 68,343 |
Excess of loss reinsurance coverage, initial and remaining |  | $ 250,592 |  |  |  |  |  |  |  | $ 250,592 |
Excess of Loss Reinsurance Transactions, Home Re Transactions |  |  |  |  |  |  |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |  |  |  |  |  |  |
Percent of reinsurance coverage threshold, option to terminate (as a percent) |  |  |  |  |  |  |  |  |  | 10.00% |
Home Re 2023-1 |  |  |  |  |  |  |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |  |  |  |  |  |  |
Term of mortgage insurance-linked notes |  |  |  | 10 years |  |  |  |  |  |  |
Initial First Layer Retention |  |  |  | $ 272,961 |  |  |  |  |  |  |
Remaining First Layer Retention |  |  |  |  |  |  |  |  |  | $ 270,109 | 272,269
Excess of loss reinsurance coverage, initial and remaining |  |  |  | $ 330,277 |  |  |  |  |  | $ 267,327 | 299,325
Reinsurance Retention Policy, Funding Percentage |  |  |  | 0.97 |  |  |  |  |  | 0.96 |
Home Re 2022-1 |  |  |  |  |  |  |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |  |  |  |  |  |  |
Term of mortgage insurance-linked notes |  |  |  |  |  | 12 years 6 months |  |  |  |  |
Initial First Layer Retention |  |  |  |  |  | $ 325,589 |  |  |  |  |
Remaining First Layer Retention |  |  |  |  |  |  |  |  |  | $ 321,021 | 322,566
Excess of loss reinsurance coverage, initial and remaining |  |  |  |  |  | $ 473,575 |  |  |  | $ 254,880 | 305,639
Reinsurance Retention Policy, Funding Percentage |  |  |  |  |  | 1 |  |  |  | 1 |
Home Re 2021-2 |  |  |  |  |  |  |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |  |  |  |  |  |  |
Term of mortgage insurance-linked notes |  |  |  |  |  |  |  | 12 years 6 months |  |  |
Initial First Layer Retention |  |  |  |  |  |  |  | $ 190,159 |  |  |
Remaining First Layer Retention |  |  |  |  |  |  |  |  |  | $ 187,496 | 188,211
Excess of loss reinsurance coverage, initial and remaining |  |  |  |  |  |  |  | $ 398,429 |  | $ 108,377 | 132,424
Reinsurance Retention Policy, Funding Percentage |  |  |  |  |  |  |  | 1 |  | 0.93 |
Home Re 2021-1 |  |  |  |  |  |  |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |  |  |  |  |  |  |
Term of mortgage insurance-linked notes |  |  |  |  |  |  |  |  | 12 years 6 months |  |
Initial First Layer Retention |  |  |  |  |  |  |  |  | $ 211,159 |  |
Remaining First Layer Retention |  |  |  |  |  |  |  |  |  | $ 209,654 | 210,027
Excess of loss reinsurance coverage, initial and remaining |  |  |  |  |  |  |  |  | $ 398,848 | $ 59,327 | $ 92,019
Reinsurance Retention Policy, Funding Percentage |  |  |  |  |  |  |  |  | 1 | 1 |

X
- Definition Amortization Period Excess of Loss Reinsurance Coverage + References No definition available. + Details
Name: | mtg_AmortizationPeriodExcessofLossReinsuranceCoverage
Namespace Prefix: | mtg_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Reinsurance Agreement, Optional Call Feature, Right To Terminate, Percent Of Reinsurance Coverage Threshold + References No definition available. + Details
Name: | mtg_ReinsuranceAgreementOptionalCallFeatureRightToTerminatePercentOfReinsuranceCoverageThreshold
Namespace Prefix: | mtg_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Reinsurance Retention Policy, Debt Issued To Cover Insurance, Term + References No definition available. + Details
Name: | mtg_ReinsuranceRetentionPolicyDebtIssuedToCoverInsuranceTerm
Namespace Prefix: | mtg_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Reinsurance Retention Policy, Excess of Loss Reinsurance Coverages + References No definition available. + Details
Name: | mtg_ReinsuranceRetentionPolicyExcessOfLossReinsuranceCoverages
Namespace Prefix: | mtg_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Reinsurance Retention Policy, Funding Percentage + References No definition available. + Details
Name: | mtg_ReinsuranceRetentionPolicyFundingPercentage
Namespace Prefix: | mtg_
Data Type: | xbrli:pureItemType
Balance Type: | na
Period Type: | instant

X
- Definition Reinsurance Retention Policy, Initial Amount Retained + References No definition available. + Details
Name: | mtg_ReinsuranceRetentionPolicyInitialAmountRetained
Namespace Prefix: | mtg_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
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_EffectsOfReinsuranceLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount per life of risk undertaken originally by insurer that is not ceded to reinsurer. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479838/944-20-50-3 + Details
Name: | us-gaap_ReinsuranceRetentionAmountRetainedPerLife
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | srt_ProductOrServiceAxis=mtg_EligibleNewInsuranceWrittenIn2026Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CededCreditRiskAxis=mtg_A2025TraditionalXOLMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CededCreditRiskAxis=mtg_A2024TraditionalXOLMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CededCreditRiskAxis=mtg_A2023TraditionalXOLMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CededCreditRiskAxis=mtg_A2022TraditionalXOLMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CededCreditRiskAxis=mtg_A2020TraditionalXOLMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CededCreditRiskAxis=mtg_ExcessOfLossReinsuranceTransactionsHomeReTransactionsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=mtg_HomeRe20231Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=mtg_HomeRe20221Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=mtg_HomeRe20212Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=mtg_HomeRe20211Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |