Equity (Details 3) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Components of accumulated other comprehensive income (loss)
Balance at beginning of period			$ 308.2
Net current period other comprehensive income (loss)	(14.7)	(14.0)	(62.1)	44.3
Balance at end of the period	246.1		246.1
Unrealized Gain on Available-for-Sale Securities
Components of accumulated other comprehensive income (loss)
Balance at beginning of period			300.8
Net current period other comprehensive income (loss)			(59.4)
Balance at end of the period	241.4		241.4
Unrealized Loss on Cash Flow Hedges
Components of accumulated other comprehensive income (loss)
Balance at beginning of period			(0.5)
Net current period other comprehensive income (loss)			0.4
Balance at end of the period	(0.1)		(0.1)
Foreign Currency Translation Adjustments
Components of accumulated other comprehensive income (loss)
Balance at beginning of period			7.9
Net current period other comprehensive income (loss)			(3.1)
Balance at end of the period	$ 4.8		$ 4.8