Employee Benefit Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Summary of net periodic pension cost
Service cost	$ 0.4	$ 0.4
Interest cost	0.7	0.6
Expected return on plan assets	(0.6)	(0.7)
Amortization of actuarial loss	0.2
Net periodic benefit cost	$ 0.7	$ 0.3