Basis of Presentation	3 Months Ended
Mar. 31, 2013
Basis of Presentation [Abstract]
Basis of Presentation	Note 1 - Basis of Presentation MGIC Investment Corporation is a holding company which, through Mortgage Guaranty Insurance Corporation ("MGIC"), MGIC Indemnity Corporation ("MIC") and several other subsidiaries, is principally engaged in the mortgage insurance business. We provide mortgage insurance to lenders throughout the United States and to government sponsored entities ("GSEs") to protect against loss from defaults on low down payment residential mortgage loans. The accompanying unaudited consolidated financial statements of MGIC Investment Corporation and its wholly-owned subsidiaries have been prepared in accordance with the instructions to Form 10-Q as prescribed by the Securities and Exchange Commission ("SEC") for interim reporting and do not include all of the other information and disclosures required by accounting principles generally accepted in the United States of America ("GAAP"). These statements should be read in conjunction with the consolidated financial statements and notes thereto for the year ended December 31, 2012 included in our Annual Report on Form 10-K. As used below, "we," "our" and "us" refer to MGIC Investment Corporation's consolidated operations or to MGIC Investment Corporation, as the context requires. In the opinion of management the accompanying financial statements include all adjustments, consisting primarily of normal recurring accruals, necessary to fairly state our financial position and results of operations for the periods indicated. The results of operations for the interim period may not be indicative of the results that may be expected for the year ending December 31, 2013. Capital The insurance laws of 16 jurisdictions, including Wisconsin, our domiciliary state, require a mortgage insurer to maintain a minimum amount of statutory capital relative to the risk in force (or a similar measure) in order for the mortgage insurer to continue to write new business. We refer to these requirements as the "Capital Requirements." While they vary among jurisdictions, the most common Capital Requirements allow for a maximum risk-to-capital ratio of 25 to 1. A risk-to-capital ratio will increase if the percentage decrease in capital exceeds the percentage decrease in insured risk. Therefore, as capital decreases, the same dollar decrease in capital will cause a greater percentage decrease in capital and a greater increase in the risk-to-capital ratio. Wisconsin does not regulate capital by using a risk-to-capital measure but instead requires a minimum policyholder position ("MPP"). The "policyholder position" of a mortgage insurer is its net worth or surplus, contingency reserve and a portion of the reserves for unearned premiums. During part of 2012 and 2013, MGIC's risk-to-capital ratio exceeded 25 to 1. In March 2013, our holding company issued additional equity and convertible debt securities and transferred $800 million to increase MGIC's capital. As a result, at March 31, 2013, MGIC's risk-to-capital ratio was 20.4 to 1, below the maximum allowed by the jurisdictions with Capital Requirements, and its policyholder position was $168 million above the required MPP of $1.2 billion. At March 31, 2013, the risk-to-capital ratio of our combined insurance operations (which includes reinsurance affiliates) was 23.1 to 1. A higher risk-to-capital ratio on a combined basis may indicate that, in order for MGIC to continue to utilize reinsurance arrangements with its subsidiaries or subsidiaries of our holding company, additional capital contributions to the reinsurance affiliates could be needed. These reinsurance arrangements permit MGIC to write insurance with a higher coverage percentage than it could on its own under certain state-specific requirements. At this time, we expect MGIC to continue to comply with the current Capital Requirements, although factors that could negatively affect such compliance are discussed throughout the financial statement footnotes. The remainder of the discussion in this footnote addresses circumstances that would be significant if we were not in such compliance. The Office of the Commissioner of Insurance of the State of Wisconsin ("OCI") has waived MGIC's compliance with Wisconsin's Capital Requirements until December 31, 2013 (the "OCI Waiver"). The OCI, in its sole discretion, may modify, terminate or extend the OCI Waiver. If the OCI modifies or terminates its waiver, or if it fails to renew its waiver upon expiration, and if MGIC does not comply with the Capital Requirements at that time, MGIC could be prevented from writing new business in all jurisdictions. We cannot assure you that MGIC will comply with the Capital Requirements in the future. If MGIC were prevented from writing new business in all jurisdictions, our insurance operations in MGIC would be in run-off (meaning no new loans would be insured but loans previously insured would continue to be covered, with premiums continuing to be received and losses continuing to be paid on those loans) until MGIC either met the Capital Requirements or obtained a necessary waiver to allow it to once again write new business. MGIC applied for waivers in the other jurisdictions with Capital Requirements and received waivers from some of them. Insurance departments, in their sole discretion, may modify, terminate or extend their waivers of Capital Requirements. If an insurance department other than the OCI modifies or terminates its waiver, or if it fails to grant a waiver or renew its waiver after expiration, and if MGIC does not comply with the Capital Requirements at that time, MGIC could be prevented from writing new business in that particular jurisdiction. New insurance written in the jurisdictions that have Capital Requirements represented approximately 50% of our new insurance written in 2012 and the first quarter of 2013. Depending on the level of losses that MGIC experiences in the future, it is possible that regulatory action by one or more jurisdictions, including those that do not have specific Capital Requirements, may prevent MGIC from continuing to write new insurance in that jurisdiction. The National Association of Insurance Commissioners ("NAIC") is reviewing the minimum capital and surplus requirements for mortgage insurers, although it has not established a date by which it must make proposals to change such requirements. Depending on the scope of proposals made by the NAIC, MGIC may be prevented from writing new business in the jurisdictions adopting such proposals. The GSEs are also developing mortgage insurer capital standards that would replace the use of external credit ratings. Revised capital standards are expected to be released in 2013, however the timing of their implementation is unknown. A possible future failure by MGIC to meet the Capital Requirements will not necessarily mean that MGIC lacks sufficient resources to pay claims on its insurance liabilities. While we believe MGIC has sufficient claims paying resources to meet its claim obligations on its insurance in force on a timely basis, we cannot assure you that events that may lead MGIC to fail to meet Capital Requirements would not also result in it not having sufficient claims paying resources. Furthermore, our estimates of MGIC's claims paying resources and claim obligations are based on various assumptions. These assumptions include the timing of the receipt of claims on loans in our delinquency inventory and future claims that we anticipate will ultimately be received, our anticipated rescission activity, premiums, housing values and unemployment rates. These assumptions are subject to inherent uncertainty and require judgment by management. Current conditions in the domestic economy make the assumptions about when anticipated claims will be received, housing values, and unemployment rates highly volatile in the sense that there is a wide range of reasonably possible outcomes. Our anticipated rescission activity is also subject to inherent uncertainty due to the difficulty of predicting the amount of claims that will be rescinded and the outcome of any legal proceedings or settlement discussions related to rescissions. Factors that could negatively affect MGIC's claims paying resources are discussed throughout the financial statement footnotes. We have in place a longstanding plan to write new business in MIC, a direct subsidiary of MGIC, if MGIC is unable to do so. During 2012, MIC began writing new business on the same policy terms as MGIC in the jurisdictions where MGIC did not have active waivers of the Capital Requirements. Because MGIC again meets the Capital Requirements, MGIC will again be writing new business in all jurisdictions and MIC will suspend writing new business. As of March 31, 2013, MIC had statutory capital of $450 million and risk in force of approximately $800 million. MIC is licensed to write business in all jurisdictions and, subject to the conditions and restrictions discussed below, has received the necessary approvals from the GSEs and the OCI to write business in all of the jurisdictions where MGIC may become unable to do so because those jurisdictions have not waived their Capital Requirements for MGIC. Under an agreement in place with Fannie Mae, as amended November 30, 2012, MIC will be eligible to write mortgage insurance through December 31, 2013, in those jurisdictions (other than Wisconsin) in which MGIC cannot write new insurance due to MGIC's failure to meet Capital Requirements and to obtain a waiver of them. MIC is also approved to write mortgage insurance for 60 days in jurisdictions that do not have Capital Requirements if a jurisdiction notifies MGIC that, due to its financial condition, it may no longer write new business. The agreement with Fannie Mae contains certain conditions and restrictions to its continued effectiveness including the continued effectiveness of the OCI Order. Under a letter from Freddie Mac that was amended and restated as of November 30, 2012, Freddie Mac approved MIC to write business only in those jurisdictions (other than Wisconsin) where either (a) MGIC is unable to write business because it does not meet the Capital Requirements and does not obtain waivers of them, or (b) MGIC receives notice that it may not write business because of that jurisdiction's view of MGIC's financial condition. This approval of MIC, which may be withdrawn at any time, expires December 31, 2013, or earlier if a financial examination by the OCI determines that there is a reasonable probability that MGIC will be unable to honor claim obligations at any time in the five years after the examination, or if MGIC fails to honor claim payments. The approval from Freddie Mac, contains certain conditions and restrictions to its continued effectiveness, including requirements that MIC not exceed a risk-to-capital ratio of 18:1 (at March 31, 2013, MIC's risk-to-capital ratio was 1.8 to 1); MGIC and MIC comply with all terms and conditions of the OCI Waiver; the OCI Waiver remain effective; and MIC provide MGIC access to the capital of MIC in an amount necessary for MGIC to maintain sufficient liquidity to satisfy its obligations under insurance policies issued by MGIC. On November 29, 2012, the OCI issued an order, effective until December 31, 2013, establishing a procedure for MIC to pay a dividend to MGIC if either of the following two events occurs: (1) an OCI examination determines that there is a reasonable probability that MGIC will be unable to honor its policy obligations at any time during the five years after the examination, or (2) MGIC fails to honor its policy obligations that it in good faith believes are valid. If one of these events occurs, the OCI is to conduct a review (to be completed within 60 days after the triggering event) to determine the maximum single dividend MIC could prudently pay to MGIC for the benefit of MGIC's policyholders, taking account of the interests of MIC's policyholders and the general public and certain standards for dividends imposed by Wisconsin law. Upon the completion of the review, the OCI will authorize, and MIC will pay, such a dividend within 30 days. We cannot assure you that the GSEs will approve or continue to approve MIC to write new business in all jurisdictions in which MGIC may become unable to do so, or that they will extend their approvals upon expiration. If one GSE does not approve MIC in all jurisdictions in which MGIC becomes unable to write new business, MIC may be able to write insurance on loans that will be sold to the other GSE or retained by private investors. However, because lenders may not know which GSE will purchase their loans until mortgage insurance has been procured, lenders may be unwilling to procure mortgage insurance from MIC. Furthermore, if we are unable to write business in all jurisdictions utilizing a combination of MGIC and MIC, lenders may be unwilling to procure insurance from us anywhere. In addition, a lender's assessment of the financial strength of our insurance operations may affect its willingness to procure insurance from us. Statement of Statutory Accounting Principles No. 101 ("SSAP No. 101") became effective January 1, 2012 and prescribed new standards for determining the amount of deferred tax assets that can be recognized as admitted assets for determining statutory capital. Under a permitted practice effective September 30, 2012 and until further notice, the OCI has approved MGIC to report its net deferred tax asset as an admitted asset in an amount not to exceed 10% of surplus as regards policyholders, notwithstanding any contrary provisions of SSAP No. 101. Deferred tax assets of $136 million and $63 million were included in MGIC's statutory capital at March 31, 2013 and December 31, 2012, respectively. Reclassifications Certain reclassifications have been made in the accompanying financial statements to 2012 amounts to conform to 2013 presentation. Subsequent events We have considered subsequent events through the date of this filing.

Note 1 - Basis of Presentation

MGIC Investment Corporation is a holding company which, through Mortgage Guaranty Insurance Corporation ("MGIC"), MGIC Indemnity Corporation ("MIC") and several other subsidiaries, is principally engaged in the mortgage insurance business. We provide mortgage insurance to lenders throughout the United States and to government sponsored entities ("GSEs") to protect against loss from defaults on low down payment residential mortgage loans.

The accompanying unaudited consolidated financial statements of MGIC Investment Corporation and its wholly-owned subsidiaries have been prepared in accordance with the instructions to Form 10-Q as prescribed by the Securities and Exchange Commission ("SEC") for interim reporting and do not include all of the other information and disclosures required by accounting principles generally accepted in the United States of America ("GAAP"). These statements should be read in conjunction with the consolidated financial statements and notes thereto for the year ended December 31, 2012 included in our Annual Report on Form 10-K. As used below, "we," "our" and "us" refer to MGIC Investment Corporation's consolidated operations or to MGIC Investment Corporation, as the context requires.

In the opinion of management the accompanying financial statements include all adjustments, consisting primarily of normal recurring accruals, necessary to fairly state our financial position and results of operations for the periods indicated. The results of operations for the interim period may not be indicative of the results that may be expected for the year ending December 31, 2013.

Capital

The insurance laws of 16 jurisdictions, including Wisconsin, our domiciliary state, require a mortgage insurer to maintain a minimum amount of statutory capital relative to the risk in force (or a similar measure) in order for the mortgage insurer to continue to write new business. We refer to these requirements as the "Capital Requirements." While they vary among jurisdictions, the most common Capital Requirements allow for a maximum risk-to-capital ratio of 25 to 1. A risk-to-capital ratio will increase if the percentage decrease in capital exceeds the percentage decrease in insured risk. Therefore, as capital decreases, the same dollar decrease in capital will cause a greater percentage decrease in capital and a greater increase in the risk-to-capital ratio. Wisconsin does not regulate capital by using a risk-to-capital measure but instead requires a minimum policyholder position ("MPP"). The "policyholder position" of a mortgage insurer is its net worth or surplus, contingency reserve and a portion of the reserves for unearned premiums.

During part of 2012 and 2013, MGIC's risk-to-capital ratio exceeded 25 to 1. In March 2013, our holding company issued additional equity and convertible debt securities and transferred $800 million to increase MGIC's capital. As a result, at March 31, 2013, MGIC's risk-to-capital ratio was 20.4 to 1, below the maximum allowed by the jurisdictions with Capital Requirements, and its policyholder position was $168 million above the required MPP of $1.2 billion. At March 31, 2013, the risk-to-capital ratio of our combined insurance operations (which includes reinsurance affiliates) was 23.1 to 1. A higher risk-to-capital ratio on a combined basis may indicate that, in order for MGIC to continue to utilize reinsurance arrangements with its subsidiaries or subsidiaries of our holding company, additional capital contributions to the reinsurance affiliates could be needed. These reinsurance arrangements permit MGIC to write insurance with a higher coverage percentage than it could on its own under certain state-specific requirements.

At this time, we expect MGIC to continue to comply with the current Capital Requirements, although factors that could negatively affect such compliance are discussed throughout the financial statement footnotes. The remainder of the discussion in this footnote addresses circumstances that would be significant if we were not in such compliance.

The Office of the Commissioner of Insurance of the State of Wisconsin ("OCI") has waived MGIC's compliance with Wisconsin's Capital Requirements until December 31, 2013 (the "OCI Waiver"). The OCI, in its sole discretion, may modify, terminate or extend the OCI Waiver. If the OCI modifies or terminates its waiver, or if it fails to renew its waiver upon expiration, and if MGIC does not comply with the Capital Requirements at that time, MGIC could be prevented from writing new business in all jurisdictions. We cannot assure you that MGIC will comply with the Capital Requirements in the future. If MGIC were prevented from writing new business in all jurisdictions, our insurance operations in MGIC would be in run-off (meaning no new loans would be insured but loans previously insured would continue to be covered, with premiums continuing to be received and losses continuing to be paid on those loans) until MGIC either met the Capital Requirements or obtained a necessary waiver to allow it to once again write new business.

MGIC applied for waivers in the other jurisdictions with Capital Requirements and received waivers from some of them. Insurance departments, in their sole discretion, may modify, terminate or extend their waivers of Capital Requirements. If an insurance department other than the OCI modifies or terminates its waiver, or if it fails to grant a waiver or renew its waiver after expiration, and if MGIC does not comply with the Capital Requirements at that time, MGIC could be prevented from writing new business in that particular jurisdiction. New insurance written in the jurisdictions that have Capital Requirements represented approximately 50% of our new insurance written in 2012 and the first quarter of 2013. Depending on the level of losses that MGIC experiences in the future, it is possible that regulatory action by one or more jurisdictions, including those that do not have specific Capital Requirements, may prevent MGIC from continuing to write new insurance in that jurisdiction. The National Association of Insurance Commissioners ("NAIC") is reviewing the minimum capital and surplus requirements for mortgage insurers, although it has not established a date by which it must make proposals to change such requirements. Depending on the scope of proposals made by the NAIC, MGIC may be prevented from writing new business in the jurisdictions adopting such proposals. The GSEs are also developing mortgage insurer capital standards that would replace the use of external credit ratings. Revised capital standards are expected to be released in 2013, however the timing of their implementation is unknown.

A possible future failure by MGIC to meet the Capital Requirements will not necessarily mean that MGIC lacks sufficient resources to pay claims on its insurance liabilities. While we believe MGIC has sufficient claims paying resources to meet its claim obligations on its insurance in force on a timely basis, we cannot assure you that events that may lead MGIC to fail to meet Capital Requirements would not also result in it not having sufficient claims paying resources. Furthermore, our estimates of MGIC's claims paying resources and claim obligations are based on various assumptions. These assumptions include the timing of the receipt of claims on loans in our delinquency inventory and future claims that we anticipate will ultimately be received, our anticipated rescission activity, premiums, housing values and unemployment rates. These assumptions are subject to inherent uncertainty and require judgment by management. Current conditions in the domestic economy make the assumptions about when anticipated claims will be received, housing values, and unemployment rates highly volatile in the sense that there is a wide range of reasonably possible outcomes. Our anticipated rescission activity is also subject to inherent uncertainty due to the difficulty of predicting the amount of claims that will be rescinded and the outcome of any legal proceedings or settlement discussions related to rescissions. Factors that could negatively affect MGIC's claims paying resources are discussed throughout the financial statement footnotes.

We have in place a longstanding plan to write new business in MIC, a direct subsidiary of MGIC, if MGIC is unable to do so. During 2012, MIC began writing new business on the same policy terms as MGIC in the jurisdictions where MGIC did not have active waivers of the Capital Requirements. Because MGIC again meets the Capital Requirements, MGIC will again be writing new business in all jurisdictions and MIC will suspend writing new business. As of March 31, 2013, MIC had statutory capital of $450 million and risk in force of approximately $800 million. MIC is licensed to write business in all jurisdictions and, subject to the conditions and restrictions discussed below, has received the necessary approvals from the GSEs and the OCI to write business in all of the jurisdictions where MGIC may become unable to do so because those jurisdictions have not waived their Capital Requirements for MGIC.

Under an agreement in place with Fannie Mae, as amended November 30, 2012, MIC will be eligible to write mortgage insurance through December 31, 2013, in those jurisdictions (other than Wisconsin) in which MGIC cannot write new insurance due to MGIC's failure to meet Capital Requirements and to obtain a waiver of them. MIC is also approved to write mortgage insurance for 60 days in jurisdictions that do not have Capital Requirements if a jurisdiction notifies MGIC that, due to its financial condition, it may no longer write new business. The agreement with Fannie Mae contains certain conditions and restrictions to its continued effectiveness including the continued effectiveness of the OCI Order.

Under a letter from Freddie Mac that was amended and restated as of November 30, 2012, Freddie Mac approved MIC to write business only in those jurisdictions (other than Wisconsin) where either (a) MGIC is unable to write business because it does not meet the Capital Requirements and does not obtain waivers of them, or (b) MGIC receives notice that it may not write business because of that jurisdiction's view of MGIC's financial condition. This approval of MIC, which may be withdrawn at any time, expires December 31, 2013, or earlier if a financial examination by the OCI determines that there is a reasonable probability that MGIC will be unable to honor claim obligations at any time in the five years after the examination, or if MGIC fails to honor claim payments. The approval from Freddie Mac, contains certain conditions and restrictions to its continued effectiveness, including requirements that MIC not exceed a risk-to-capital ratio of 18:1 (at March 31, 2013, MIC's risk-to-capital ratio was 1.8 to 1); MGIC and MIC comply with all terms and conditions of the OCI Waiver; the OCI Waiver remain effective; and MIC provide MGIC access to the capital of MIC in an amount necessary for MGIC to maintain sufficient liquidity to satisfy its obligations under insurance policies issued by MGIC.

On November 29, 2012, the OCI issued an order, effective until December 31, 2013, establishing a procedure for MIC to pay a dividend to MGIC if either of the following two events occurs: (1) an OCI examination determines that there is a reasonable probability that MGIC will be unable to honor its policy obligations at any time during the five years after the examination, or (2) MGIC fails to honor its policy obligations that it in good faith believes are valid. If one of these events occurs, the OCI is to conduct a review (to be completed within 60 days after the triggering event) to determine the maximum single dividend MIC could prudently pay to MGIC for the benefit of MGIC's policyholders, taking account of the interests of MIC's policyholders and the general public and certain standards for dividends imposed by Wisconsin law. Upon the completion of the review, the OCI will authorize, and MIC will pay, such a dividend within 30 days.

We cannot assure you that the GSEs will approve or continue to approve MIC to write new business in all jurisdictions in which MGIC may become unable to do so, or that they will extend their approvals upon expiration. If one GSE does not approve MIC in all jurisdictions in which MGIC becomes unable to write new business, MIC may be able to write insurance on loans that will be sold to the other GSE or retained by private investors. However, because lenders may not know which GSE will purchase their loans until mortgage insurance has been procured, lenders may be unwilling to procure mortgage insurance from MIC. Furthermore, if we are unable to write business in all jurisdictions utilizing a combination of MGIC and MIC, lenders may be unwilling to procure insurance from us anywhere. In addition, a lender's assessment of the financial strength of our insurance operations may affect its willingness to procure insurance from us.

Statement of Statutory Accounting Principles No. 101 ("SSAP No. 101") became effective January 1, 2012 and prescribed new standards for determining the amount of deferred tax assets that can be recognized as admitted assets for determining statutory capital. Under a permitted practice effective September 30, 2012 and until further notice, the OCI has approved MGIC to report its net deferred tax asset as an admitted asset in an amount not to exceed 10% of surplus as regards policyholders, notwithstanding any contrary provisions of SSAP No. 101. Deferred tax assets of $136 million and $63 million were included in MGIC's statutory capital at March 31, 2013 and December 31, 2012, respectively.

Reclassifications

Certain reclassifications have been made in the accompanying financial statements to 2012 amounts to conform to 2013 presentation.

Subsequent events

We have considered subsequent events through the date of this filing.