Employee Retirement Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Components of net retirement cost
Service cost	$ 0.2	$ 0.2	$ 0.4	$ 0.5
Interest	4.9	4.9	9.7	9.8
Expected return on plan assets	(5.8)	(5.7)	(11.4)	(11.4)
Actuarial loss	0.9	0.5	1.8	1.0
Defined benefit expense	0.2	(0.1)	0.5	(0.1)
Profit sharing	3.2	2.2	5.8	4.5
Net expense	$ 3.4	$ 2.1	$ 6.3	$ 4.4