XML 21 R42.htm IDEA: XBRL DOCUMENT v2.4.1.9
Fair Value Measurements (Details) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
U.S. Treasury securities and obligations of U.S. government corporations and agencies $ 312,805mtg_USTreasurySecuritiesAndObligationsOfUSGovernmentCorporationsAndAgenciesFairValueDisclosure $ 346,775mtg_USTreasurySecuritiesAndObligationsOfUSGovernmentCorporationsAndAgenciesFairValueDisclosure
Obligations of U.S. states and political subdivisions 952,703mtg_ObligationsOfUSStatesAndPoliticalSubdivisionsFairValueDisclosure 855,142mtg_ObligationsOfUSStatesAndPoliticalSubdivisionsFairValueDisclosure
Corporate debt securities 2,408,016mtg_CorporateDebtSecuritiesFairValueDisclosure 2,425,281mtg_CorporateDebtSecuritiesFairValueDisclosure
Asset-backed securities 253,919mtg_AssetBackedSecuritiesFairValueDisclosure 286,655mtg_AssetBackedSecuritiesFairValueDisclosure
Residential mortgage-backed securities 309,031mtg_ResidentialMortgageBackedSecuritiesFairValueDisclosure 321,237mtg_ResidentialMortgageBackedSecuritiesFairValueDisclosure
Commercial mortgage-backed securities 260,606mtg_CommercialMortgageBackedSecuritiesFairValueDisclosure 275,278mtg_CommercialMortgageBackedSecuritiesFairValueDisclosure
Collateralized loan obligations 60,544mtg_CollateralizedLoanObligationsFairValueDisclosure 60,076mtg_CollateralizedLoanObligationsFairValueDisclosure
Debt securities issued by foreign sovereign governments 37,039mtg_DebtSecuritiesIssuedByForeignSovereignGovernmentsFairValueDisclosure 39,170mtg_DebtSecuritiesIssuedByForeignSovereignGovernmentsFairValueDisclosure
Total debt securities 4,594,663mtg_TotalDebtSecuritiesFairValueDisclosure 4,609,614mtg_TotalDebtSecuritiesFairValueDisclosure
Equity securities 3,100mtg_EquitySecuritiesFairValueDisclocure 3,055mtg_EquitySecuritiesFairValueDisclocure
Total investments 4,597,763us-gaap_AvailableForSaleSecurities 4,612,669us-gaap_AvailableForSaleSecurities
Real estate acquired 10,897us-gaap_OtherAssetsFairValueDisclosure [1] 12,658us-gaap_OtherAssetsFairValueDisclosure [1]
Par Value [Member]    
Debt [Abstract]    
Senior Notes 61,953us-gaap_NotesPayableFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= mtg_ParValueMember		 61,953us-gaap_NotesPayableFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= mtg_ParValueMember
Convertible Senior Notes due 2017 345,000mtg_ConvertibleSeniorNotesDueOneFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= mtg_ParValueMember		 345,000mtg_ConvertibleSeniorNotesDueOneFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= mtg_ParValueMember
Convertible Senior Notes due 2020 500,000mtg_ConvertibleSeniorNotesDueTwoFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= mtg_ParValueMember		 500,000mtg_ConvertibleSeniorNotesDueTwoFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= mtg_ParValueMember
Convertible Junior Subordinated Debentures 389,522us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= mtg_ParValueMember		 389,522us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= mtg_ParValueMember
Total Debt 1,296,475us-gaap_DebtInstrumentFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= mtg_ParValueMember		 1,296,475us-gaap_DebtInstrumentFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= mtg_ParValueMember
Fair Value [Member]    
Debt [Abstract]    
Senior Notes 63,309us-gaap_NotesPayableFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember		 63,618us-gaap_NotesPayableFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
Convertible Senior Notes due 2017 382,622mtg_ConvertibleSeniorNotesDueOneFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember		 387,997mtg_ConvertibleSeniorNotesDueOneFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
Convertible Senior Notes due 2020 735,945mtg_ConvertibleSeniorNotesDueTwoFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember		 735,075mtg_ConvertibleSeniorNotesDueTwoFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
Convertible Junior Subordinated Debentures 497,221us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember		 500,201us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
Total Debt 1,679,097us-gaap_DebtInstrumentFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember		 1,686,891us-gaap_DebtInstrumentFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
U.S. Treasury securities and obligations of U.S. government corporations and agencies 189,913mtg_USTreasurySecuritiesAndObligationsOfUSGovernmentCorporationsAndAgenciesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member		 188,824mtg_USTreasurySecuritiesAndObligationsOfUSGovernmentCorporationsAndAgenciesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
Obligations of U.S. states and political subdivisions 0mtg_ObligationsOfUSStatesAndPoliticalSubdivisionsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member		 0mtg_ObligationsOfUSStatesAndPoliticalSubdivisionsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
Corporate debt securities 0mtg_CorporateDebtSecuritiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member		 0mtg_CorporateDebtSecuritiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
Asset-backed securities 0mtg_AssetBackedSecuritiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member		 0mtg_AssetBackedSecuritiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
Residential mortgage-backed securities 0mtg_ResidentialMortgageBackedSecuritiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member		 0mtg_ResidentialMortgageBackedSecuritiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
Commercial mortgage-backed securities 0mtg_CommercialMortgageBackedSecuritiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member		 0mtg_CommercialMortgageBackedSecuritiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
Collateralized loan obligations 0mtg_CollateralizedLoanObligationsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member		 0mtg_CollateralizedLoanObligationsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
Debt securities issued by foreign sovereign governments 37,039mtg_DebtSecuritiesIssuedByForeignSovereignGovernmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member		 39,170mtg_DebtSecuritiesIssuedByForeignSovereignGovernmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
Total debt securities 226,952mtg_TotalDebtSecuritiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member		 227,994mtg_TotalDebtSecuritiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
Equity securities 2,779mtg_EquitySecuritiesFairValueDisclocure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member		 2,734mtg_EquitySecuritiesFairValueDisclocure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
Total investments 229,731us-gaap_AvailableForSaleSecurities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member		 230,728us-gaap_AvailableForSaleSecurities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
Real estate acquired 0us-gaap_OtherAssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member		 [1] 0us-gaap_OtherAssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member		 [1]
Debt [Abstract]    
Senior Notes 0us-gaap_NotesPayableFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member		 0us-gaap_NotesPayableFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
Convertible Senior Notes due 2017 0mtg_ConvertibleSeniorNotesDueOneFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member		 0mtg_ConvertibleSeniorNotesDueOneFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
Convertible Senior Notes due 2020 0mtg_ConvertibleSeniorNotesDueTwoFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member		 0mtg_ConvertibleSeniorNotesDueTwoFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
Convertible Junior Subordinated Debentures 0us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member		 0us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
Total Debt 0us-gaap_DebtInstrumentFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member		 0us-gaap_DebtInstrumentFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
Significant Other Observable Inputs (Level 2) [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
U.S. Treasury securities and obligations of U.S. government corporations and agencies 122,892mtg_USTreasurySecuritiesAndObligationsOfUSGovernmentCorporationsAndAgenciesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member		 157,951mtg_USTreasurySecuritiesAndObligationsOfUSGovernmentCorporationsAndAgenciesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
Obligations of U.S. states and political subdivisions 950,912mtg_ObligationsOfUSStatesAndPoliticalSubdivisionsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member		 853,296mtg_ObligationsOfUSStatesAndPoliticalSubdivisionsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
Corporate debt securities 2,408,016mtg_CorporateDebtSecuritiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member		 2,425,281mtg_CorporateDebtSecuritiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
Asset-backed securities 253,919mtg_AssetBackedSecuritiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member		 286,655mtg_AssetBackedSecuritiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
Residential mortgage-backed securities 309,031mtg_ResidentialMortgageBackedSecuritiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member		 321,237mtg_ResidentialMortgageBackedSecuritiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
Commercial mortgage-backed securities 260,606mtg_CommercialMortgageBackedSecuritiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member		 275,278mtg_CommercialMortgageBackedSecuritiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
Collateralized loan obligations 60,544mtg_CollateralizedLoanObligationsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member		 60,076mtg_CollateralizedLoanObligationsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
Debt securities issued by foreign sovereign governments 0mtg_DebtSecuritiesIssuedByForeignSovereignGovernmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member		 0mtg_DebtSecuritiesIssuedByForeignSovereignGovernmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
Total debt securities 4,365,920mtg_TotalDebtSecuritiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member		 4,379,774mtg_TotalDebtSecuritiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
Equity securities 0mtg_EquitySecuritiesFairValueDisclocure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member		 0mtg_EquitySecuritiesFairValueDisclocure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
Total investments 4,365,920us-gaap_AvailableForSaleSecurities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member		 4,379,774us-gaap_AvailableForSaleSecurities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
Real estate acquired 0us-gaap_OtherAssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member		 [1] 0us-gaap_OtherAssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member		 [1]
Debt [Abstract]    
Senior Notes 63,309us-gaap_NotesPayableFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member		 63,618us-gaap_NotesPayableFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
Convertible Senior Notes due 2017 382,622mtg_ConvertibleSeniorNotesDueOneFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member		 387,997mtg_ConvertibleSeniorNotesDueOneFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
Convertible Senior Notes due 2020 735,945mtg_ConvertibleSeniorNotesDueTwoFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member		 735,075mtg_ConvertibleSeniorNotesDueTwoFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
Convertible Junior Subordinated Debentures 497,221us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member		 500,201us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
Total Debt 1,679,097us-gaap_DebtInstrumentFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member		 1,686,891us-gaap_DebtInstrumentFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
Significant Unobservable Inputs (Level 3) [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
U.S. Treasury securities and obligations of U.S. government corporations and agencies 0mtg_USTreasurySecuritiesAndObligationsOfUSGovernmentCorporationsAndAgenciesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member		 0mtg_USTreasurySecuritiesAndObligationsOfUSGovernmentCorporationsAndAgenciesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
Obligations of U.S. states and political subdivisions 1,791mtg_ObligationsOfUSStatesAndPoliticalSubdivisionsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member		 1,846mtg_ObligationsOfUSStatesAndPoliticalSubdivisionsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
Corporate debt securities 0mtg_CorporateDebtSecuritiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member		 0mtg_CorporateDebtSecuritiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
Asset-backed securities 0mtg_AssetBackedSecuritiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member		 0mtg_AssetBackedSecuritiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
Residential mortgage-backed securities 0mtg_ResidentialMortgageBackedSecuritiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member		 0mtg_ResidentialMortgageBackedSecuritiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
Commercial mortgage-backed securities 0mtg_CommercialMortgageBackedSecuritiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member		 0mtg_CommercialMortgageBackedSecuritiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
Collateralized loan obligations 0mtg_CollateralizedLoanObligationsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member		 0mtg_CollateralizedLoanObligationsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
Debt securities issued by foreign sovereign governments 0mtg_DebtSecuritiesIssuedByForeignSovereignGovernmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member		 0mtg_DebtSecuritiesIssuedByForeignSovereignGovernmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
Total debt securities 1,791mtg_TotalDebtSecuritiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member		 1,846mtg_TotalDebtSecuritiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
Equity securities 321mtg_EquitySecuritiesFairValueDisclocure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member		 321mtg_EquitySecuritiesFairValueDisclocure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
Total investments 2,112us-gaap_AvailableForSaleSecurities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member		 2,167us-gaap_AvailableForSaleSecurities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
Real estate acquired 10,897us-gaap_OtherAssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member		 [1] 12,658us-gaap_OtherAssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member		 [1]
Debt [Abstract]    
Senior Notes 0us-gaap_NotesPayableFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member		 0us-gaap_NotesPayableFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
Convertible Senior Notes due 2017 0mtg_ConvertibleSeniorNotesDueOneFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member		 0mtg_ConvertibleSeniorNotesDueOneFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
Convertible Senior Notes due 2020 0mtg_ConvertibleSeniorNotesDueTwoFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member		 0mtg_ConvertibleSeniorNotesDueTwoFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
Convertible Junior Subordinated Debentures 0us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member		 0us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
Total Debt $ 0us-gaap_DebtInstrumentFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member		 $ 0us-gaap_DebtInstrumentFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
[1] Real estate acquired through claim settlement, which is held for sale, is reported in Other Assets on the consolidated balance sheet.