Statutory Information - Narrative (Details) $ in Millions	1 Months Ended	9 Months Ended
	Oct. 31, 2025 USD ($)	Sep. 30, 2025 USD ($) jurisdiction
Statutory capital requirements [Abstract]
Number of jurisdictions with risk-to-capital requirements (in jurisdictions) | jurisdiction		16
Mortgage Guaranty Insurance Corporation
Statutory capital requirements [Abstract]
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 Corp		$ 400
Mortgage Guaranty Insurance Corporation | Subsequent Event
Statutory capital requirements [Abstract]
Dividend paid to MGIC Investment Corp	$ 400