Accounting Policies (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021	Nov. 30, 2020	Nov. 03, 2020
Statutory Accounting Practices
Debt instrument, face amount	$ 155.3		$ 155.3	$ 155.3
Interest rate			5.25%	5.25%
Equity components of the convertible notes	$ 40.8
Shares included in weighted-average diluted shares	4,173	4,200
Paid-in Capital
Statutory Accounting Practices
Equity components of the convertible notes			$ 39.2	$ 39.2
Retained Earnings
Statutory Accounting Practices
Equity components of the convertible notes			$ 6.7	$ 6.7
ASU 2020-06
Statutory Accounting Practices
Diluted earnings per share	$ 13.73
Decreased by diluted earnings per share	$ 0.84