XML 88 R57.htm IDEA: XBRL DOCUMENT
v3.6.0.2

Loss Reserves - Prior Year Loss Reserves (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |
Prior years | $ (147,658) | $ (110,302) | $ (100,359)
Decrease in estimated claim rate on primary defaults |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |
Prior years | (148,000) | (141,000) | (43,000)
Increase (decrease) in estimated severity on primary defaults |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |
Prior years | 9,000 | 43,000 | (35,000)
Change in estimates related to pool reserves, LAE reserves, reinsurance and other |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |
Prior years | $ (9,000) | $ (12,000) | $ (22,000)

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_LiabilityForClaimsAndClaimsAdjustmentExpenseLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of expense (reversal of expense) for claims incurred in prior reporting periods and related claims settlement costs. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 235 -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-18) -URI http://asc.fasb.org/extlink&oid=34713774&loc=d3e575016-122915 + Details
Name: | us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_NoncatastrophicEventAxis=mtg_IncreaseDecreaseInExpectedClaimRateMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_NoncatastrophicEventAxis=mtg_IncreaseDecreaseInEstimatedSeverityPrimaryDefaultsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_NoncatastrophicEventAxis=mtg_IncreaseDecreaseRelatedToPoolReservesLaeReservesAndReinsuranceMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |