SCHEDULE II - CONDENSED FINANCIAL INFORMATION OF REGISTRANT - SUPPLEMENTARY NOTES (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Senior Notes | 5.25% Senior Notes due 2028
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Stated interest rate (in hundredths)	5.25%
Insurance Subsidiaries
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Percentage of statutory policyholders surplus used to determine maximum allowable dividends	10.00%
Adjusted statutory net income measurement period	3 years
Adjusted statutory net income dividend payment measurement period	2 years
Proceeds from contribution from holding company	$ 0	$ 0	$ 0
Mortgage Guaranty Insurance Corporation
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Dividends paid to the holding company	600,000,000	800,000,000	400,000,000
Proceeds from contribution from holding company	$ 0	$ 0	$ 0