Financial Instruments (Details 2) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Summary of Contractual Maturities: Available-for-Sale Securities
Due in one year or less, amortized cost	$ 2,002.4	$ 1,541.1
Due in one year or less, estimated fair value	2,006.0	1,541.7
Due after one year through five years, amortized cost	982.9	868.2
Due after one year through five years, estimated fair value	993.7	870.2
Due after five years, amortized cost	18.7	23.8
Due after five years, estimated fair value	19.3	24.0
Estimated Fair Value	3,004.0	2,433.1
Amortized Cost	$ 3,019.0	$ 2,435.9