Statutory Information - Surplus contributions and dividends of insurance subsidiaries (Details) - Mortgage Guaranty Insurance Corporation - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Related Party Transaction [Line Items]
Dividends paid to the parent company	$ 400,000	$ 390,000	$ 280,000
Dividend to parent, distribution of investment in subsidiary	$ 8,900
Dividend to parent, distribution of interest in 9% Debentures		$ 139,500