Debt - Carrying Value and Principal Amount at Maturity of Junior Convertible Securities (Details) - Junior convertible securities - Junior Convertible Trust Preferred Securities - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Carrying Value	$ 299.5	$ 318.4
Principal Amount at Maturity	$ 401.0	$ 430.8
Debt instrument term	16 years	16 years