Investments - Contractual Maturities of Bonds (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Cost or Amortized Cost
Due in one year or less	$ 1.1
Due after one year through five years	70.2
Due after five years through ten years	0.0
Due after ten years	0.0
Cost or Amortized Cost	71.3	$ 6.4
Fair Value
Due in one year or less	1.1
Due after one year through five years	70.1
Due after five years through ten years	0.0
Due after ten years	0.0
Fair Value	$ 71.2	$ 6.6