Pension and Other Postretirement Benefits (Tables)

9 Months Ended

Jan. 31, 2012

Pension and Other Postretirement Benefits [Abstract]

Pension and other postretirement benefit expense

	Three Months Ended						Nine Months Ended
	January 31,						January 31,
(Dollars in millions)	2011			2012			2011			2012
Pension Benefits:
Service cost	$	3.9		$	4.0		$	11.7		$	12.0
Interest cost		8.3			8.5			25.0			25.5
Expected return on plan assets		(9.1	)		(10.0	)		(27.2	)		(30.3	)
Amortization of:
Prior service cost		0.2			0.2			0.7			0.7
Net actuarial loss		4.7			4.8			14.0			14.5
Net expense	$	8.0		$	7.5		$	24.2		$	22.4
Other Postretirement Benefits:
Service cost	$	0.3		$	0.4		$	1.0		$	1.1
Interest cost		0.8			0.7			2.4			2.3
Amortization of:
Prior service cost		—			0.2			—			0.4
Net actuarial loss		—			—			0.1			—
Net expense	$	1.1		$	1.3		$	3.5		$	3.8