Description of Business - Mortgage (Details) - Mortgage - USD ($) $ in Billions	Dec. 31, 2022	Dec. 31, 2021
Business Overview [Abstract]
Down payment percent of purchase price	20.00%
Equity in home (percent)	20.00%
Direct primary mortgage insurance in force	$ 261.0	$ 246.0
Direct primary mortgage insurance risk in force	$ 66.1	$ 60.9