Pension and Other Postretirement Benefits (Tables)

3 Months Ended

Jul. 31, 2012

Pension and Other Postretirement Benefits [Abstract]

Pension and other postretirement benefit expense

	Three Months Ended
	July 31
(Dollars in millions)	2011			2012
Pension Benefits:
Service cost	$	4.0		$	4.9
Interest cost		8.5			8.8
Expected return on plan assets		(10.1	)		(10.2	)
Amortization of:
Prior service cost		0.2			0.2
Net actuarial loss		4.9			7.0
Net expense	$	7.5		$	10.7
Other Postretirement Benefits:
Service cost	$	0.4		$	0.4
Interest cost		0.8			0.7
Amortization of:
Prior service cost		0.1			0.2
Net expense	$	1.3		$	1.3