XML 55 R40.htm IDEA: XBRL DOCUMENT
v3.19.2

Reinsurance Reinsurance - Variable Interest Entity (Details) - USD ($) $ in Thousands | 6 Months Ended |
--- | --- | ---
Jun. 30, 2019 | Dec. 31, 2018
Home Re special purpose insurers |  |
Effects of Reinsurance [Line Items] |  |
Term of mortgage insurance-linked notes | 10 years |
Remaining First Layer Retention | $ 354,421 |
Remaining Excess of Loss Reinsurance Coverages | 634,375 |
Home Re 2018-1 |  |
Effects of Reinsurance [Line Items] |  |
Remaining First Layer Retention | 168,691 |
Remaining Excess of Loss Reinsurance Coverages | 318,636 |
Total VIE Assets | 318,636 | $ 318,636
Home Re 2019-1 |  |
Effects of Reinsurance [Line Items] |  |
Remaining First Layer Retention | 185,730 |
Remaining Excess of Loss Reinsurance Coverages | 315,739 |
Total VIE Assets | $ 315,739 |

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, Remaining Excess of Loss Reinsurance Coverages + References No definition available. + Details
Name: | mtg_ReinsuranceRetentionPolicyRemainingExcessOfLossReinsuranceCoverages
Namespace Prefix: | mtg_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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 Stated amount that is the upper retention limit per entity policy. + References No definition available. + Details
Name: | us-gaap_ReinsuranceRetentionPolicyAmountRetained
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Carrying amount of the assets in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the Variable Interest Entity (VIE), where the reporting entity is not the VIE's primary beneficiary. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph a -URI http://asc.fasb.org/extlink&oid=118582676&loc=d3e5728-111685 + Details
Name: | us-gaap_VariableInterestEntityNonconsolidatedCarryingAmountAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

X
- Details
Name: | dei_LegalEntityAxis=mtg_HomeRe20181Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=mtg_HomeRe20191Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |