Stockholders' Equity (Computation Of Basic And Diluted EPS) (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Basic earnings per share:
Net earnings allocated to common shares	$ 97.8	$ 114.7	$ 152.0	$ 210.4
Weighted average number of common shares outstanding	157.5	173.0	158.9	174.7
Basic earnings per share	$ 0.62	$ 0.66	$ 0.96	$ 1.20
Diluted earnings per share:
Net earnings allocated to common shares	$ 97.8	$ 114.7	$ 152.0	$ 210.4
Weighted average number of common shares outstanding	157.5	173.0	158.9	174.7
Incremental shares from assumed conversions of share-based awards	2.8	3.0	3.2	3.6
Adjusted weighted average number of common shares outstanding	160.3	176.0	162.1	178.3
Diluted earnings per share	$ 0.61	$ 0.65	$ 0.94	$ 1.18