Business Overview [Abstract]

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- Definition

Mortgage Insurance [Abstract]

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- Definition

This element represents the maximum down payment percentage on a home's purchase price that is used to measure the need for private mortgage insurance.

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No definition available.

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- Definition

This element represents the maximum equity-ownership percentage on a home's value that is used to measure the need for private mortgage insurance for refinancings.

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No definition available.

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- Definition

Reduction in Number of New Defaults from the Prior Quarter

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Risk In Force

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- Definition

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

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
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Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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-Section 50
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Amount of participating insurance in force.

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Note 1 - Business Overview and Recent Developments (Details) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2020 USD ($) segment	May 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Business Overview [Abstract]
Number of Reportable Business Segments \| segment		2
Mortgage Insurance [Abstract]
Reduction in Number of New Defaults from the Prior Quarter	(0.675)
Senior Notes Due 2025 \| Senior Notes
Mortgage Insurance [Abstract]
Debt Instrument, Face Amount			$ 525,000
Mortgage segment
Mortgage Insurance [Abstract]
Private Mortgage Insurance Protects Lenders For Loans Made With Less Than This Maximum Down Payment Percentage	20.00%	20.00%
Private Mortgage Insurance Protects Lenders For Refinancings Made to Home Buyers With Less Than This Maximum Equity-Ownership Percentage	20.00%	20.00%
Direct Primary Mortgage Insurance in Force	$ 245,500,000	$ 245,500,000		$ 240,600,000
Direct Primary Mortgage Insurance RIF	61,000,000	61,000,000		60,900,000
Credit Risk Transfer Transactions \| Mortgage segment
Mortgage Insurance [Abstract]
Direct Primary Mortgage Insurance RIF	$ 389,100	$ 389,100		$ 275,200