Financial Instruments (Details 3) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Investments, Debt and Equity Securities [Abstract]
Proceeds from maturities and sales	$ 2,362.2	$ 2,387.9	$ 5,185.8	$ 3,363.4
Realized gains	1.1	0.7	2.1	1.3
Realized losses	$ (1.1)	$ (2.0)	$ (2.7)	$ (2.9)