Share-based Compensation (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Estimated share-based compensation expense	$ 8.7		$ 8.7
Share-based Compensation Expense [Abstract]
Share-based Compensation Expense	1.7	$ 1.6	$ 5.9	$ 5.6
Number of options granted (in shares)			861,500
Weighted-average grant-date fair value per share of options granted (dollars per share)			$ 2.41
Number of options exercised (in shares)			2,733
Stock Options [Member]
Share-based Compensation Expense [Abstract]
Share-based Compensation Expense	0.3	0.3	$ 1.5	1.3
Restricted Stock [Member]
Share-based Compensation Expense [Abstract]
Share-based Compensation Expense	0.5	0.4	$ 2.6	2.3
Number of shares granted (in shares)			862,300
Weighted average grant date fair value, granted (dollars per share)			$ 4.10
Intrinsic value of shares vested/restrictions lapsed during the period			$ 2.9
Restricted Stock Units Issued to Directors [Member]
Share-based Compensation Expense [Abstract]
Share-based Compensation Expense	0.3	0.2	0.6	0.5
Performance Share Awards [Member]
Share-based Compensation Expense [Abstract]
Share-based Compensation Expense	$ 0.6	$ 0.7	$ 1.2	$ 1.5
Number of shares granted (in shares)			890,700
Weighted average grant date fair value, granted (dollars per share)			$ 3.09