Employee Benefits (Tables)

9 Months Ended

Sep. 30, 2012

Compensation and Retirement Disclosure [Abstract]

Pension and Other Postretirement Benefit Costs

	Pension
	Three Months Ended						Nine Months Ended
	September 30,						September 30,
	2012			2011			2012			2011
	(in millions)
Service cost	$	1.1		$	0.7		$	3.0		$	2.1
Interest cost	1.3			1.2			3.7			3.4
Expected return on plan assets	(0.9		)	(0.7		)	(2.7		)	(1.9		)
Amortization of prior service costs	1.3			1.4			3.9			4.0
Amortization of actuarial loss	0.6			—			1.0			—
Periodic expense	$	3.4		$	2.6		$	8.9		$	7.6

	Postretirement benefits
	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2012		2011		2012		2011
	(in millions)
Service cost	$	0.1	$	0.1	$	0.1	$	0.1
Interest cost	—		—		0.2		0.2
Expected return on plan assets	—		—		—		—
Amortization of prior service costs	0.1		0.1		0.3		0.3
Recognized net actuarial loss	—		—		—		—
Periodic expense	$	0.2	$	0.2	$	0.6	$	0.6