XML 53 R39.htm IDEA: XBRL DOCUMENT
v3.20.2

Reinsurance - Summary of Quota Reinsurance Arrangements (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended |  |
--- | --- | --- | --- | ---
Sep. 30, 2020 | Sep. 30, 2019 | Sep. 30, 2020 | Sep. 30, 2019 | Dec. 31, 2019 | Dec. 31, 2018
Effects of Reinsurance [Line Items] |  |  |  |  |  |
Ceded losses incurred | $ 20,707 | $ 2,736 | $ 65,462 | $ 7,841 |  |
Reinsurance recoverable on loss reserves | 83,143 | 19,566 | 83,143 | 19,566 | $ 21,641 | $ 33,328
Quota Share Reinsurance Agreements, Excluding Captive Agreements |  |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |  |
Ceded premiums written and earned, net of profit commission | 43,448 | 23,032 | 131,651 | 87,721 |  |
Ceded losses incurred | 20,707 | 2,729 | 65,493 | 7,845 |  |
Ceding commissions | 12,128 | 11,042 | 35,518 | 37,807 |  |
Profit commission | 17,191 | $ 32,177 | 45,939 | 108,079 |  |
Reinsurance recoverable on loss reserves | $ 83,100 |  | $ 83,100 |  | $ 21,600 |
Quota Share Reinsurance Agreement, 2015 |  |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |  |
Contingent termination fee |  |  |  | $ 6,800 |  |

X
- Definition Ceded Premiums Written and Earned, Net of Profit Commission + References No definition available. + Details
Name: | mtg_CededPremiumsWrittenandEarnedNetofProfitCommission
Namespace Prefix: | mtg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Reinsurance Ceding Commission Earned + References No definition available. + Details
Name: | mtg_ReinsuranceCedingCommissionEarned
Namespace Prefix: | mtg_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Reinsurance, Profit Commission + References No definition available. + Details
Name: | mtg_ReinsuranceProfitCommission
Namespace Prefix: | mtg_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Reinsurance, Quota Share Reinsurance Agreement, Terms, Contingent Termination Fee + References No definition available. + Details
Name: | mtg_ReinsuranceQuotaShareReinsuranceAgreementTermsContingentTerminationFee
Namespace Prefix: | mtg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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 of reduction of provision for policy benefits and costs incurred for policies ceded. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 20 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=99397103&loc=d3e6811-158387 + Details
Name: | us-gaap_ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountCeded
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
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 http://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 http://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 http://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 http://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_ReinsurancePolicyTypeAxis=mtg_QuotaShareReinsuranceAgreementsExcludingCaptivesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ReinsurancePolicyTypeAxis=mtg_QuotaShareReinsuranceAgreement2015Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |