Short-term Investments (Contractual Maturities Of Investments In Debt Securities Available-For-Sale) (Details) $ in Millions	Jun. 30, 2015 USD ($)
Amortized Cost
Due within one year	$ 583.1
Due after one year up to two years	499.5
Due after two years up to three years	471.1
Due after three years up to four years	7.3
Asset-backed securities	231.2
Amortized Cost	1,792.2
Fair Value
Due within one year	583.5
Due after one year up to two years	500.4
Due after two years up to three years	471.5
Due after three years up to four years	7.3
Asset-backed securities	231.2
Fair Value	$ 1,793.9