XML 50 R38.htm IDEA: XBRL DOCUMENT
v3.24.3

Reinsurance - Narrative (Details) - USD ($) $ in Thousands | 9 Months Ended |  |  |
--- | --- | --- | --- | ---
Sep. 30, 2024 | Dec. 31, 2023 | Sep. 30, 2023 | Dec. 31, 2022
Effects of Reinsurance [Line Items] |  |  |  |
Reinsurance recoverable on loss reserves | $ 45,327 | $ 33,302 | $ 40,934 | $ 28,240
Most New Insurance Written In 2025 And 2026 |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |
Reinsurance, quota share reinsurance agreement, terms, quota share, percent | 40.00% |  |  |
Quota Share Reinsurance Transactions |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |
Ceding commission, percentage (as a percent) | 20.00% |  |  |
Reinsurance, quote share reinsurance agreement, annual loss ratio cap (as a percent) | 300.00% |  |  |
Reinsurance, quota reinsurance agreement, lifetime loss ratio cap (as a percent) | 200.00% |  |  |
Threshold for private mortgage insurer eligibility requirements for termination election (less than) (as a percent) | 90.00% |  |  |
Reinsurance recoverable on loss reserves | $ 45,300 | $ 33,300 |  |
Credit Union QSR Transaction |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |
Threshold for private mortgage insurer eligibility requirements for termination election (less than) (as a percent) | 80.00% |  |  |
Reinsurance, quota share reinsurance agreement, terms, quota share, percent | 65.00% |  |  |
Home Re special purpose insurers |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |
Percent of total trust assets invested in cash or direct U.S. federal government obligations | 99.50% |  |  |

X
- Definition Reinsurance, Quota Share Reinsurance Agreement, Terms, Annual Loss Ratio Cap + References No definition available. + Details
Name: | mtg_ReinsuranceQuotaShareReinsuranceAgreementTermsAnnualLossRatioCap
Namespace Prefix: | mtg_
Data Type: | dtr-types1:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Reinsurance, Quota Share Reinsurance Agreement, Terms, Ceding Commission, Percent + References No definition available. + Details
Name: | mtg_ReinsuranceQuotaShareReinsuranceAgreementTermsCedingCommissionPercent
Namespace Prefix: | mtg_
Data Type: | dtr-types1:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Reinsurance, Quota Share Reinsurance Agreement, Terms, Lifetime Loss Ratio Cap + References No definition available. + Details
Name: | mtg_ReinsuranceQuotaShareReinsuranceAgreementTermsLifetimeLossRatioCap
Namespace Prefix: | mtg_
Data Type: | dtr-types1:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Reinsurance, Quota Share Reinsurance Agreement, Terms, Quota Share, Percent + References No definition available. + Details
Name: | mtg_ReinsuranceQuotaShareReinsuranceAgreementTermsQuotaSharePercent
Namespace Prefix: | mtg_
Data Type: | dtr-types1:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Reinsurance, Quota Share Reinsurance Agreement, Terms, Threshold For Private Mortgage Insurer Eligibility Requirements For Termination Election + References No definition available. + Details
Name: | mtg_ReinsuranceQuotaShareReinsuranceAgreementTermsThresholdForPrivateMortgageInsurerEligibilityRequirementsForTerminationElection
Namespace Prefix: | mtg_
Data Type: | dtr-types1:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Reinsurance Retention Policy, Percent Of Total Trust Assets Invested In Cash Or Direct U.S. Federal Government Obligations + References No definition available. + Details
Name: | mtg_ReinsuranceRetentionPolicyPercentOfTotalTrustAssetsInvestedInCashOrDirectU.S.FederalGovernmentObligations
Namespace Prefix: | mtg_
Data Type: | dtr-types1:percentItemType
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_EffectsOfReinsuranceLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount, after valuation allowance, recoverable under reinsurance contracts for losses reported to the ceding insurer but not yet paid and amounts expected for incurred losses and settlement expenses, which have not yet been reported to the ceding insurer. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 7 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480046/944-40-55-7 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 9E -Publisher FASB -URI https://asc.fasb.org/1943274/2147480046/944-40-55-9E Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (cc) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480081/944-40-50-3 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480081/944-40-50-3 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 4C -Publisher FASB -URI https://asc.fasb.org/1943274/2147480081/944-40-50-4C Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 310 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147477363/944-310-50-2 Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479838/944-20-50-5 Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 310 -Name Accounting Standards Codification -Section 45 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org/1943274/2147477409/944-310-45-6 + Details
Name: | us-gaap_ReinsuranceRecoverableForUnpaidClaimsAndClaimsAdjustments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | srt_ProductOrServiceAxis=mtg_MostNewInsuranceWrittenIn2025And2026Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

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

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