Employee Retirement Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Components of net retirement cost
Service cost	$ 0.2	$ 0.2	$ 0.6	$ 0.7
Interest	4.9	4.9	14.6	14.7
Expected return on plan assets	(5.7)	(5.7)	(17.1)	(17.1)
Actuarial loss	0.7	0.4	2.5	1.4
Prior service cost	0.1	0.1	0.1	0.1
Defined benefit expense	0.2	(0.1)	0.7	(0.2)
Profit sharing	3.1	1.9	8.9	6.4
Net expense	$ 3.3	$ 1.8	$ 9.6	$ 6.2