Long-Duration Insurance Contracts - Deferred Sale Inducement Costs, Rollforward (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Movement in Deferred Sales Inducements [Roll Forward]
Balance, beginning of period	$ 15.9	$ 17.3
Capitalizations	0.0	0.0
Amortization expense	(1.0)	(1.2)
Experience adjustment	(0.8)	(0.2)
Balance, end of period	$ 14.1	$ 15.9