Share-based Compensation (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Estimated share-based compensation expense					$ 14.5
Share-based Compensation Expense [Abstract]
Share-based Compensation Expense	2.3	2.9	12.0	11.8
Number of options granted (in shares)			495,650
Weighted-average grant-date fair value per share of options granted			$ 4.31
Number of options exercised (in shares)			0
Stock Options [Member]
Share-based Compensation Expense [Abstract]
Share-based Compensation Expense	0.1	0.4	2.2	1.9
Restricted Stock [Member]
Share-based Compensation Expense [Abstract]
Share-based Compensation Expense	0.6	1.0	4.7	4.9
Number of shares granted (in shares)			527,060
Weighted average grant date fair value, granted (dollars per share)			$ 8.79
Fair value of shares vested/restrictions lapsed during the period			6.9
Restricted Stock Units Issued to Directors [Member]
Share-based Compensation Expense [Abstract]
Share-based Compensation Expense	0.2	0.3	0.6	0.7
Performance Share Awards [Member]
Share-based Compensation Expense [Abstract]
Share-based Compensation Expense	$ 1.4	$ 1.2	$ 4.5	$ 4.3
Number of shares granted (in shares)			577,450
Weighted average grant date fair value, granted (dollars per share)			$ 9.90