Employee Retirement Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Components of Net Retirement Cost
Service cost	$ 0.3	$ 0.2
Interest	4.7	4.8
Expected return on plan assets	(6.6)	(5.6)
Amortization of actuarial loss	1.2	0.9
Defined benefit expense	(0.4)	0.3
Profit sharing	3.1	2.6
Net expense	$ 2.7	$ 2.9