Stock Option Activity (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Stock options outstanding as of January 1, 2012	18.1
Granted	0.6
Exercised	(1.2)	(1.3)	(0.5)
Cancelled/expired	(3.0)
Forfeited	(0.4)
Stock options outstanding as of December 31, 2012	14.1	18.1
Stock options outstanding as of Jan 1, 2012, Weighted-average exercise price	$ 12.10
Granted, Weighted-average exercise price	$ 11.65
Exercised, Weighted-average exercise price	$ 9.43
Cancelled/expired, Weighted-average exercise price	$ 25.20
Forfeited, Weighted-average exercise price	$ 4.93
Stock options outstanding as of Dec 31, 2012, Weighted-average exercise price	$ 9.76	$ 12.10
Stock options outstanding, Weighted-average remaining contractual term	4 years 6 months
Stock options outstanding, Aggregate intrinsic value	$ 27.6
Stock options vested and expected to vest, Outstanding	13.4
Stock options vested and expected to vest, Weighted-average exercise price	$ 9.92
Stock options vested and expected to vest, Weighted-average remaining contractual term	4 years 5 months
Stock options vested and expected to vest, Aggregate intrinsic value	24.4
Stock options exercisable, Number	10.2
Stock options exercisable, Weighted-average exercise price	$ 10.89
Stock options exercisable, Weighted-average remaining contractual term	3 years 7 months
Stock options exercisable, Aggregate intrinsic value	9.9
Non-vested as of January 1, 2012	5.0
Granted	0.6
Vested	(1.3)
Forfeited	(0.4)
Non-vested as of December 31, 2012	3.9	5.0
Non-vested as of January 1, 2012, Weighted-average grant date fair value	$ 3.31
Granted, Weighted-average grant date fair value	$ 4.24	$ 4.57	$ 3.88
Vested, Weighted-average grant date fair value	$ 3.94
Forfeited, Weighted-average grant date fair value	$ 2.88
Non-vested as of December 31, 2012, Weighted-average grant date fair value	$ 3.29	$ 3.31
Non-vested options outstanding, Weighted-average remaining contractual term	7 years
Non-vested options outstanding, Aggregate intrinsic value	18.0
Intrinsic value of stock options exercised	2.0	3.2	0.6
Cash received from stock options exercised	$ 11.7	$ 13.3	$ 4.8