XML 64 R40.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Reinsurance - Summary of Quota Reinsurance Arrangements (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017
Effects of Reinsurance [Line Items] |  |  |  |
Ceded losses incurred | $ (508) | $ 5,469 | $ 3,810 | $ 14,486
Quota Share Reinsurance Agreements, Excluding Captive Agreements |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |
Ceded premiums written and earned, net of profit commission | 25,248 | 30,880 | 79,716 | 88,692
Ceded losses incurred | (522) | 5,879 | 3,531 | 14,990
Ceding commissions | 12,983 | 12,500 | 38,268 | 36,751
Profit commission | $ 39,664 | $ 31,621 | $ 111,622 | $ 95,063

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, 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 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 fees and commissions from financial services and banking activities and correspondent clearing. Includes fees from depositor accounts, credit cards, merchant discounts, and fiduciary and trust activities, guarantee fees, investment advisory, management, and administrative fees, transfer agent fees, and insurance commissions. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.13) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
Name: | us-gaap_FeesAndCommissions
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of reduction of provision for policy benefits and costs incurred for policies ceded. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 20 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6480758&loc=d3e6811-158387 + Details
Name: | us-gaap_ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountCeded
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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