Debt (Details 1) (Convertible subordinated notes, USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Convertible subordinated notes
Total interest expenses recognized on the convertible subordinated notes
Coupon rate interest	$ 4.4	$ 4.4	$ 13.1	$ 13.1
Amortized debt discount	3.1	2.9	9.1	8.4
Total interest expenses recognized on the convertible subordinated notes	$ 7.5	$ 7.3	$ 22.2	$ 21.5