XML 68 R40.htm IDEA: XBRL DOCUMENT
v3.20.1

Litigation and Contingencies (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2020 | Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract] |  |
Average paid claim reduction due to curtailments (as a percent) | 4.40% | 5.00%
Maximum exposure associated with other discussions and legal proceedings | $ 47 |

X
- Definition Average paid claim reduction due to curtailments. + References No definition available. + Details
Name: | mtg_AveragePaidClaimsReductionDueToCurtailments
Namespace Prefix: | mtg_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Estimated maximum exposure associated with other discussions and legal proceedings related to claims paying practices. + References No definition available. + Details
Name: | mtg_MaximumExposureAssociatedWithOtherDiscussionsLegalProceedings
Namespace Prefix: | mtg_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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