The income earned from investments in securities and property, equipment and other capital assets. It includes rent from property and equipment, dividends from shares in corporations, and interest from bonds, loans, mortgages, derivatives, commercial paper, bank accounts, certificates of deposits, treasuries, and other financial securities. It does not include realized gains and losses on investments or investment expenses.

No definition available.

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- Definition

Amount of expenses related to the generation of investment income.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-04.2)

-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.9)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

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- Definition

Amount, after investment expense, of income earned from investments in securities and real estate. Includes, but is not limited to, real estate investment, policy loans, dividends, and interest. Excludes realized gain (loss) on investments.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 16

-Article 12

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-04.2)

-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 2

-Article 7

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Investments, Investment Income By Category (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income									$ 90,554mtg_GrossInvestmentIncome	$ 83,425mtg_GrossInvestmentIncome	$ 124,201mtg_GrossInvestmentIncome
Investment expenses									(2,907)	(2,686)	(2,561)
Net investment income	23,956us-gaap_NetInvestmentIncome	22,355us-gaap_NetInvestmentIncome	21,180us-gaap_NetInvestmentIncome	20,156us-gaap_NetInvestmentIncome	21,278us-gaap_NetInvestmentIncome	20,250us-gaap_NetInvestmentIncome	20,883us-gaap_NetInvestmentIncome	18,328us-gaap_NetInvestmentIncome	87,647us-gaap_NetInvestmentIncome	80,739us-gaap_NetInvestmentIncome	121,640us-gaap_NetInvestmentIncome
Fixed Maturities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income									89,437	82,168	122,886
Equity Securities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income									227	229	200
Cash Equivalents [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income									179	353	333
Other [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income									$ 711	$ 675	$ 782