XML 70 R46.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Investments - Securities In Unrealized Loss Position (Details) - USD ($) $ in Thousands | Sep. 30, 2018 | Dec. 31, 2017
--- | --- | ---
Continuous Unrealized Loss Portion, Fair Value [Abstract] |  |
Less Than 12 Months | $ 2,875,083 |
12 Months or Greater | 933,768 |
Total | 3,808,851 |
Continuous Unrealized Loss Portion, Unrealized Loses [Abstract] |  |
Less Than 12 Months | (45,073) |
12 Months or Greater | (46,765) |
Total | (91,838) |
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] |  |
Less Than 12 Months |  | $ 1,667,170
12 Months or Greater |  | 752,693
Total |  | 2,419,863
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Reportable Items [Abstract] |  |
Less Than 12 Months |  | (9,357)
12 Months or Greater |  | (22,206)
Total |  | (31,563)
U.S. Treasury securities and obligations of U.S. government corporations and agencies |  |
Continuous Unrealized Loss Portion, Fair Value [Abstract] |  |
Less Than 12 Months | 89,759 |
12 Months or Greater | 78,769 |
Total | 168,528 |
Continuous Unrealized Loss Portion, Unrealized Loses [Abstract] |  |
Less Than 12 Months | (583) |
12 Months or Greater | (2,770) |
Total | (3,353) |
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] |  |
Less Than 12 Months |  | 144,042
12 Months or Greater |  | 31,196
Total |  | 175,238
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Reportable Items [Abstract] |  |
Less Than 12 Months |  | (796)
12 Months or Greater |  | (482)
Total |  | (1,278)
Obligations of U.S. states and political subdivisions |  |
Continuous Unrealized Loss Portion, Fair Value [Abstract] |  |
Less Than 12 Months | 643,147 |
12 Months or Greater | 245,763 |
Total | 888,910 |
Continuous Unrealized Loss Portion, Unrealized Loses [Abstract] |  |
Less Than 12 Months | (12,356) |
12 Months or Greater | (9,252) |
Total | (21,608) |
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] |  |
Less Than 12 Months |  | 505,311
12 Months or Greater |  | 211,684
Total |  | 716,995
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Reportable Items [Abstract] |  |
Less Than 12 Months |  | (3,624)
12 Months or Greater |  | (5,125)
Total |  | (8,749)
Corporate debt securities |  |
Continuous Unrealized Loss Portion, Fair Value [Abstract] |  |
Less Than 12 Months | 1,782,640 |
12 Months or Greater | 299,549 |
Total | 2,082,189 |
Continuous Unrealized Loss Portion, Unrealized Loses [Abstract] |  |
Less Than 12 Months | (29,184) |
12 Months or Greater | (13,121) |
Total | (42,305) |
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] |  |
Less Than 12 Months |  | 932,350
12 Months or Greater |  | 200,716
Total |  | 1,133,066
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Reportable Items [Abstract] |  |
Less Than 12 Months |  | (4,288)
12 Months or Greater |  | (4,881)
Total |  | (9,169)
Asset backed securities (“ABS”) |  |
Continuous Unrealized Loss Portion, Fair Value [Abstract] |  |
Less Than 12 Months | 70,935 |
12 Months or Greater | 0 |
Total | 70,935 |
Continuous Unrealized Loss Portion, Unrealized Loses [Abstract] |  |
Less Than 12 Months | (546) |
12 Months or Greater | 0 |
Total | (546) |
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] |  |
Less Than 12 Months |  | 4,923
12 Months or Greater |  | 0
Total |  | 4,923
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Reportable Items [Abstract] |  |
Less Than 12 Months |  | (2)
12 Months or Greater |  | 0
Total |  | (2)
Residential mortgage backed securities (“RMBS”) |  |
Continuous Unrealized Loss Portion, Fair Value [Abstract] |  |
Less Than 12 Months | 4,930 |
12 Months or Greater | 149,648 |
Total | 154,578 |
Continuous Unrealized Loss Portion, Unrealized Loses [Abstract] |  |
Less Than 12 Months | (183) |
12 Months or Greater | (11,411) |
Total | (11,594) |
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] |  |
Less Than 12 Months |  | 14,979
12 Months or Greater |  | 166,329
Total |  | 181,308
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Reportable Items [Abstract] |  |
Less Than 12 Months |  | (280)
12 Months or Greater |  | (7,084)
Total |  | (7,364)
Commercial mortgage backed securities (“CMBS”) |  |
Continuous Unrealized Loss Portion, Fair Value [Abstract] |  |
Less Than 12 Months | 81,972 |
12 Months or Greater | 160,039 |
Total | 242,011 |
Continuous Unrealized Loss Portion, Unrealized Loses [Abstract] |  |
Less Than 12 Months | (1,763) |
12 Months or Greater | (10,211) |
Total | (11,974) |
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] |  |
Less Than 12 Months |  | 51,096
12 Months or Greater |  | 138,769
Total |  | 189,865
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Reportable Items [Abstract] |  |
Less Than 12 Months |  | (358)
12 Months or Greater |  | (4,548)
Total |  | (4,906)
Collateralized loan obligations (“CLO”) |  |
Continuous Unrealized Loss Portion, Fair Value [Abstract] |  |
Less Than 12 Months | 201,700 |
12 Months or Greater | 0 |
Total | 201,700 |
Continuous Unrealized Loss Portion, Unrealized Loses [Abstract] |  |
Less Than 12 Months | (458) |
12 Months or Greater | 0 |
Total | $ (458) |
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] |  |
Less Than 12 Months |  | 14,243
12 Months or Greater |  | 3,568
Total |  | 17,811
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Reportable Items [Abstract] |  |
Less Than 12 Months |  | (7)
12 Months or Greater |  | (72)
Total |  | (79)
Equity securities |  |
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] |  |
Less Than 12 Months |  | 226
12 Months or Greater |  | 431
Total |  | 657
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Reportable Items [Abstract] |  |
Less Than 12 Months |  | (2)
12 Months or Greater |  | (14)
Total |  | $ (16)

X
- Definition Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss + References No definition available. + Details
Name: | mtg_DebtSecuritiesAvailableforsaleContinuousUnrealizedLossPosition12MonthsorLongerAccumulatedLoss
Namespace Prefix: | mtg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value + References No definition available. + Details
Name: | mtg_DebtSecuritiesAvailableforsaleContinuousUnrealizedLossPosition12MonthsorLongerFairValue
Namespace Prefix: | mtg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss + References No definition available. + Details
Name: | mtg_DebtSecuritiesAvailableforsaleContinuousUnrealizedLossPositionLessthan12MonthsAccumulatedLoss
Namespace Prefix: | mtg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value + References No definition available. + Details
Name: | mtg_DebtSecuritiesAvailableforsaleContinuousUnrealizedLossPositionLessthan12MonthsFairValue
Namespace Prefix: | mtg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss + References No definition available. + Details
Name: | mtg_DebtSecuritiesAvailableforsaleUnrealizedLossPositionAccumulatedLoss
Namespace Prefix: | mtg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value + References No definition available. + Details
Name: | mtg_DebtSecuritiesAvailableforsaleUnrealizedLossPositionFairValue
Namespace Prefix: | mtg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value [Abstract] + References No definition available. + Details
Name: | mtg_DebtSecuritiesAvailableforsaleUnrealizedLossPositionFairValueAbstract
Namespace Prefix: | mtg_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for twelve months or longer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27290-111563 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27337-111563 + Details
Name: | us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale in a continuous loss position. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27337-111563 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27290-111563 + Details
Name: | us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition This item represents the aggregate fair value of investments in debt and equity securities in an unrealized loss position which are categorized neither as held-to-maturity nor trading securities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27290-111563 + Details
Name: | us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValueAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for less than twelve months. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27290-111563 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27337-111563 + Details
Name: | us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition This item represents the aggregate fair value of investments in debt and equity securities categorized neither as held-to-maturity nor trading securities that have been in a continuous unrealized loss position for less than twelve months. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27337-111563 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27290-111563 + Details
Name: | us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition This item represents the aggregate fair value of investments in debt and equity securities categorized neither as held-to-maturity nor trading securities that have been in a continuous unrealized loss position for twelve months or longer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27290-111563 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27337-111563 + Details
Name: | us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_OtherThanTemporaryImpairmentLossesInvestmentsAvailableforsaleSecuritiesReportableItemsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_USTreasuryAndGovernmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_USStatesAndPoliticalSubdivisionsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_AssetBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_ResidentialMortgageBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_CommercialMortgageBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_CollateralizedLoanObligationsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_EquitySecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |