XML 48 R37.htm IDEA: XBRL DOCUMENT
v3.23.1

Reinsurance - Narrative (Details) - USD ($) $ in Thousands | 3 Months Ended |  |  |
--- | --- | --- | --- | ---
Mar. 31, 2023 | Dec. 31, 2022 | Mar. 31, 2022 | Dec. 31, 2021
Effects of Reinsurance [Line Items] |  |  |  |
Reinsurance recoverable on loss reserves | $ 32,761 | $ 28,240 | $ 64,717 | $ 66,905
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 | $ 32,800 | $ 28,200 |  |
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% |  |  |
Aggregate Excess of Loss Reinsurance Transactions, Home Re | Minimum |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |
Amortization period excess of loss reinsurance coverage | 10 years |  |  |
Aggregate Excess of Loss Reinsurance Transactions, Home Re | Maximum |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |
Amortization period excess of loss reinsurance coverage | 12 years 6 months |  |  |
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 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, Quota Share Reinsurance Agreement, Terms, Annual Loss Ratio Cap + References No definition available. + Details
Name: | mtg_ReinsuranceQuotaShareReinsuranceAgreementTermsAnnualLossRatioCap
Namespace Prefix: | mtg_
Data Type: | dtr-types: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-types: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-types:percentItemType
Balance Type: | na
Period Type: | instant

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-types: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-types: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/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 310 -Section 45 -Paragraph 6 -URI https://asc.fasb.org/extlink&oid=99404803&loc=d3e21412-158489 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 20 -Section 50 -Paragraph 5 -URI https://asc.fasb.org/extlink&oid=99397103&loc=d3e6824-158387 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (a) -URI https://asc.fasb.org/extlink&oid=116884095&loc=d3e14764-158437 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (cc) -URI https://asc.fasb.org/extlink&oid=116884095&loc=d3e14764-158437 + Details
Name: | us-gaap_ReinsuranceRecoverableForUnpaidClaimsAndClaimsAdjustments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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: | us-gaap_CededCreditRiskAxis=mtg_AggregateExcessOfLossReinsuranceTransactionsHomeReEntitiesMember
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: |

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