Corporate Investments and Funds Held For Clients (Expected Maturities Of Available-For-Sale Securities) (Details) $ in Millions	Dec. 31, 2019 USD ($)
Corporate Investments And Funds Held For Clients [Abstract]
One year or less	$ 5,248.5
One year to two years	5,107.8
Two years to three years	4,930.4
Three years to four years	3,740.3
After four years	5,774.1
Total available-for-sale securities	$ 24,801.1