Statutory Information (Details) $ in Millions	1 Months Ended	9 Months Ended
	Oct. 31, 2023 USD ($)	Sep. 30, 2023 USD ($) jurisdiction
Statutory capital requirements [Abstract]
Number of jurisdictions with risk-to-capital requirements (in jurisdictions) | jurisdiction		16
Maximum permitted risk-to-capital ratio commonly applied		25 to 1
Mortgage Guaranty Insurance Corporation
Statutory capital requirements [Abstract]
Maximum risk-to-capital ratio		25
Risk to capital ratio at end of period		9.6 to 1
Risk-to-capital ratio		9.6
Amount of policyholders position above or below required MPP		$ 3,800
Amount of required MPP		$ 2,100
Percentage of statutory policyholders surplus used to determine maximum allowable dividends (as a percent)		10.00%
Adjusted statutory net income measurement period (in years)		3 years
Adjusted statutory net income dividend payment measurement period (in years)		2 years
Dividend paid to MGIC Investment Corporation		$ 300
Mortgage Guaranty Insurance Corporation | Subsequent Event
Statutory capital requirements [Abstract]
Dividend paid to MGIC Investment Corporation	$ 300