Employee Benefit Plans (Net Postretirement Benefit Expense) (Details) (Postretirement Benefits Other Than Pensions [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Postretirement Benefits Other Than Pensions [Member]
Service cost	$ 0.1	$ 0.1	$ 0.1
Interest cost	0.3	0.4	0.5
Amortization of prior service cost	(0.1)	(0.1)	(0.1)
Amortization of net loss	0.1	0.1	0.2
Net postretirement benefit expense	$ 0.4	$ 0.5	$ 0.7