Retirement Benefits (Narrative) (Details) (USD $) In Millions, 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, 2011
Supplemental Employee Retirement Plans, Defined Benefit [Member]
Expenses towards non-qualified supplemental retirement plan	$ 0.6	$ 0.7	$ 1.9	$ 2.1
Other liabilities for non-qualified plan	28.9		28.9		28.5
Accumulated other comprehensive loss net of tax			5.3		5.7
Deferred Compensation Plans [Member]
Employer contributions to the plans	2.5	2.4	7.9	8.2
Liability for the plans	$ 10.4		$ 10.4		$ 10.7