Employee Benefit Plans (Details 3) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Pension Benefits [Member]
Components of net periodic benefit cost
Service cost	$ 5.4	$ 5.0	$ 5.6
Interest cost	17.8	17.6	17.5
Expected return on plan assets	(19.0)	(19.5)	(16.7)
Amortization of prior service cost	0.4	0.5	0.5
Recognized actuarial loss	7.0	5.1	8.9
Settlements and curtailments	1.7	1.4	1.0
Net periodic benefit cost	13.3	10.1	16.8
Other Benefits [Member]
Components of net periodic benefit cost
Service cost	0.8	0.6	0.5
Interest cost	0.9	0.8	0.8
Amortization of prior service cost	(1.9)	(1.9)	(1.9)
Recognized actuarial loss	1.2	1.2	1.2
Settlements and curtailments			(0.6)
Net periodic benefit cost	$ 1.0	$ 0.7