Corporate Investments and Funds Held For Clients (Expected Maturities Of Available-For-Sale Securities) (Details) $ in Millions	Sep. 30, 2019 USD ($)
Corporate Investments And Funds Held For Clients [Abstract]
One year or less	$ 4,713.6
One year to two years	6,040.5
Two years to three years	4,743.3
Three years to four years	3,726.7
After four years	5,421.9
Total available-for-sale securities	$ 24,646.0