Debt (Details 1) (Convertible subordinated notes [Member], USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Convertible subordinated notes [Member]
Total interest expenses recognized on the convertible subordinated notes
Coupon rate interest	$ 4.3	$ 4.3	$ 8.7	$ 8.7
Amortized debt discount	3.0	2.8	6.0	5.5
Total interest expenses recognized on the convertible subordinated notes	$ 7.3		$ 14.7	$ 14.2