Income Taxes (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2010
Current:
Federal	$ 67.0	$ (14.4)	$ 26.2
State	11.2	7.7	(0.5)
Foreign	49.1	40.9	44.2
Total current	127.3	34.2	69.9
Deferred:
Federal	4.7	37.7	24.6
State	(0.7)	3.1	4.3
Foreign	(2.3)	0.1	(0.7)
Total deferred	1.7	40.9	28.2
Income tax provision	$ 129.0	$ 75.1	$ 98.1