Retirement Benefit 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 pension expense
Service cost	$ 6.1	$ 7.2	$ 12.9	$ 14.1
Interest cost	4.6	5.2	9.6	10.2
Expected return on plan assets	(8.2)	(8.0)	(16.5)	(15.8)
Settlement	0.7		0.7
Amortization of prior service cost	(1.2)	(0.2)	(1.4)	(0.4)
Amortization of unrecognized actuarial loss	3.3	1.8	6.7	3.7
Net periodic benefit cost	$ 5.3	$ 6.0	$ 12.0	$ 11.8