Significant Accounting Policies - Narrative (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($) payment segment group	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) $ / shares
Significant Accounting Policies Line Items [Line Items]
Maximum maturity duration for short term investment grouping	12 months
Number of payments missed for insured loans | payment	2
Second-lien reserve for premium deficiency		$ 0.1
Percent of LTV at which HPA must be canceled automatically	0.78
Number of reportable segments | segment	2
Depreciation, depletion and amortization	$ 15.9	18.3	$ 20.8
homegenius
Significant Accounting Policies Line Items [Line Items]
Number of reportable segments | segment	1
Minimum
Significant Accounting Policies Line Items [Line Items]
Number of payments missed for insured loans | payment	2
Useful life	3 years
Maximum
Significant Accounting Policies Line Items [Line Items]
Term of contract	12 months
Useful life	7 years
Mortgage
Significant Accounting Policies Line Items [Line Items]
Number of mortgage insurance product categories | group	2
Premium receivable for deferred monthly premiums	$ 30.3	29.7
Contractual deferred monthly premiums	$ 74.0	$ 77.0
Increase in net premium earned			$ 32.9
Increase in net premiums earned per share | $ / shares			$ 0.12