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Mortgage Insurance [Abstract]

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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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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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Risk In Force

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

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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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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Amount of participating insurance in force.

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Amount, after effects of policies assumed or ceded, of expense related to the provision for policy benefits and costs incurred.

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Note 1 - Condensed Consolidated Financial Statements - Business Overview and Significant Accounting Policies Business Overview (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) segment	Jun. 30, 2019 USD ($)	May 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Business Overview [Abstract]
Number of Reportable Business Segments \| segment			2
Mortgage Insurance [Abstract]
Net income (loss)	$ (29,951)	$ 166,730	$ 110,510	$ 337,687
Provision for losses	$ 304,418	$ 47,427	$ 340,369	$ 68,181
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	$ 241,300,000		$ 241,300,000
Direct Primary Mortgage Insurance RIF	60,300,000		60,300,000
Credit Risk Transfer Transactions \| Mortgage segment
Mortgage Insurance [Abstract]
Direct Primary Mortgage Insurance RIF	$ 325,100		$ 325,100			$ 275,200