Employee Benefit Plans (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Components of net periodic benefit costs:
Service cost	$ 5.5	$ 3.9	$ 4.2
Interest cost	4.9	4.4	5.3
Expected return on plan assets	(4.1)	(3.4)	(3.5)
Amortization of prior service costs	1.3	0.6	1.0
Net periodic benefit costs	7.6	5.5	7.0
Change in benefit obligation:
Benefit obligation at beginning of year	151.7	124.9
Service cost	5.5	3.9	4.2
Interest cost	4.9	4.4	5.3
Plan participant contributions	3.4	2.7
Benefits paid	(3.3)	(4.2)
Actuarial loss (gain)	(7.7)	11.1
Impact of foreign currency exchange rates	(1.0)	8.9
Benefit obligation at end of year	153.5	151.7	124.9
Change in plan assets:
Fair value of plan assets at beginning of year	111.3	95.7
Actuarial return on plan assets	(2.1)	1.8
Plan participant and employer contributions	7.6	7.4
Benefits paid	(3.3)	(4.2)
Impact of foreign currency exchange rates	(0.6)	10.6
Fair value of plan assets at end of year	112.9	111.3	95.7
Net funded status	(40.6)	(40.4)
Accumulated benefit obligation	145.5	144.8
Amounts recognized in the accompanying consolidated balance sheets:
Current liabilities	(1.4)	(1.0)
Non-current liabilities	(39.2)	(39.4)
Net benefit obligation	(40.6)	(40.4)
Pre-tax amounts recognized in accumulated other comprehensive income:
Net gain (loss)	(22.2)	(25.8)
Accumulated other comprehensive income (loss)	(22.2)	(25.8)
Accumulated contributions in excess of net periodic benefit cost	(18.4)	(14.6)
Net amount recognized	$ (40.6)	$ (40.4)