Corporate Investments And Funds Held For Clients (Expected Maturities Of Available-For-Sale Securities) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012
Corporate Investments And Funds Held For Clients [Abstract]
Due in one year or less	$ 2,984.5
Due after one year up to two years	1,617.1
Due after two years up to three years	3,435.2
Due after three years up to four years	4,054.4
Due after four years	6,002.2
Total available-for-sale securities	$ 18,093.4