The number of shares of the company's common stock to which each Right initially entitles a shareholder to purchase.

No definition available.

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- Definition

The minimum percentage of beneficial ownership of the company's common stock by any person, by itself or together with its affiliates and associates, required to be considered an Acquiring Person as defined in the Shareholder Rights Agreement.

+ References

No definition available.

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- Definition

The description of the Distribution Date as per the Shareholder Rights Agreement.

+ References

No definition available.

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- Definition

The stated purchase price for which a shareholder is initially entitled to purchase a full share of the company's common stock under the Shareholder Rights Agreement.

+ References

No definition available.

+ Details

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- Definition

The stated purchase price for which a shareholder is initially entitled to purchase a one-tenth share of the company's common stock under the Shareholder Rights Agreement.

+ References

No definition available.

+ Details

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- Definition

The price, per Right, at which each Right is redeemable at any time prior to the time a person becomes an Acquiring Person.

+ References

No definition available.

+ Details

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- Definition

The dollar amount received by the entity for each share of common stock issued or sold in the stock transaction.

+ References

No definition available.

+ Details

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- Definition

The number of shareholder rights accompanying each outstanding share of the company's common stock under the Shareholder Rights Agreement.

+ References

No definition available.

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- Definition

Additions to the surplus of a subsidiary from parent company funds.

+ References

No definition available.

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- Definition

The maximum number of common shares permitted to be issued by an entity's charter and bylaws.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.29)

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 30

-Article 5

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- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

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-SubTopic 30

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-Paragraph 8

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

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-Subparagraph (SX 210.5-02.22(a)(1))

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- Definition

Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of convertible debt securities using the if-converted method.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 260

-SubTopic 10

-Section 50

-Paragraph 1

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-Topic 260

-SubTopic 10

-Section 45

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-Subparagraph (c)

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- Definition

The cash inflow from the additional capital contribution to the entity.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

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-Topic 230

-SubTopic 10

-Section 45

-Paragraph 14

-Subparagraph (a)

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- Definition

Number of new stock issued during the period.

+ References

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

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-Subparagraph (SX 210.3-04)

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-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 29, 30

-Article 5

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Shareholders' Equity (Details) (USD $)	1 Months Ended	12 Months Ended
Shareholders' Equity (Details) (USD $)	Mar. 31, 2013	Dec. 31, 2014 Right	Dec. 31, 2013	Dec. 31, 2012	Jun. 30, 2013	Apr. 30, 2012
Shareholders' Equity [Abstract]
Common stock, shares authorized (in shares)		1,000,000,000us-gaap_CommonStockSharesAuthorized	1,000,000,000us-gaap_CommonStockSharesAuthorized		680,000,000us-gaap_CommonStockSharesAuthorized	460,000,000us-gaap_CommonStockSharesAuthorized
Debt Instrument [Line Items]
Stated interest rate (in hundredths)		2.00%
Shareholder Rights Agreement [Abstract]
Shareholder rights accompanying each outstanding share of the company's common stock (in number of Rights)		1
Distribution date, description		The earlier of ten days after a public announcement that a person has become an Acquiring Person, or ten business days after a person announces or begins a tender offer in which consummation of such offer would result in a person becoming an Acquiring Person.
Common stock, beneficial ownership threshold to be considered an Acquiring Person (in hundredths)		5.00%
Common shares purchasable per Right (in shares)		0.1
Purchase price (in dollars per share)		$ 14mtg_PurchasePricePerFullShare
Purchase price (in dollars per one-tenth share)		$ 1.40mtg_PurchasePricePerOneTenthShare
Redemption price (in dollars per Right)		$ 0.001mtg_RedemptionPriceInDollarsPerRight
Sale of common stock (in shares)	135,000,000
Sale of common stock, price per share (in dollars per share)	$ 5.15mtg_SaleOfCommonStockPricePerShare
Sale of common stock, net proceeds	$ 663,300,000	$ 0	$ 663,335,000	$ 0
Mortgage Guaranty Insurance Corporation [Member]
Subsidiary or Equity Method Investee [Line Items]
Surplus contributions made to subsidiary by the parent company	800,000,000	0	800,000,000	100,000,000
Convertible Debentures [Member]
Debt Instrument [Line Items]
Outstanding principal amount		389,500,000	389,500,000
Stated interest rate (in hundredths)		9.00%	9.00%
Shares reserved for conversion under convertible debt (in shares)		28,900,000
Convertible Senior Notes [Member]
Debt Instrument [Line Items]
Outstanding principal amount		345,000,000	345,000,000
Stated interest rate (in hundredths)		5.00%	5.00%
Shares reserved for conversion under convertible debt (in shares)		97,600,000
Convertible Senior Notes - Due April 2020 [Member]
Debt Instrument [Line Items]
Outstanding principal amount	$ 500,000,000	$ 500,000,000	$ 500,000,000
Stated interest rate (in hundredths)	2.00%	2.00%	2.00%