Consolidated Statements of Stockholders' Equity (USD $) In Millions, unless otherwise specified	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss) Foreign Currency Translation Adjustment	Accumulated Other Comprehensive Income (Loss) Unrealized Gain (Loss) on Securities Available for Sale, Net of Taxes	Treasury Stock, at Cost
Beginning Balance at Mar. 31, 2009	$ 1,048.5	$ 2.5	$ 881.2	$ 1,985.4	$ (17.4)	$ (8.1)	$ (1,795.1)
Beginning Balance, shares at Mar. 31, 2009		249.1
Comprehensive income:
Net earnings	406.1			406.1
Foreign currency translation adjustment, net of tax (benefit) provision of $(2.6), $1.4 and $4.2 for 2012, 2011 and 2010, respectively	27.8				27.8
Unrealized gain on securities available for sale, net of tax (benefit) provision of $(0.2), $0.6 and $1.4 for 2012, 2011 and 2010, respectively	3.1					3.1
Treasury stock purchases	(288.1)						(288.1)
Shares issued/forfeited for share-based compensation	89.2		(16.9)	(2.2)			108.3
Share-based compensation expense	89.3		89.3
Tax benefit of share-based compensation expense	11.8		11.8
Ending Balance at Mar. 31, 2010	1,387.7	2.5	965.4	2,389.3	10.4	(5.0)	(1,974.9)
Ending Balance, shares at Mar. 31, 2010		249.1
Comprehensive income:
Net earnings	456.2			456.2
Foreign currency translation adjustment, net of tax (benefit) provision of $(2.6), $1.4 and $4.2 for 2012, 2011 and 2010, respectively	24.1				24.1
Unrealized gain on securities available for sale, net of tax (benefit) provision of $(0.2), $0.6 and $1.4 for 2012, 2011 and 2010, respectively	2.5					2.5
Treasury stock purchases	(464.1)						(464.1)
Shares issued/forfeited for share-based compensation	130.1		(14.4)	(0.3)			144.8
Share-based compensation expense	109.2		109.2
Tax benefit of share-based compensation expense	17.2		17.2
Ending Balance at Mar. 31, 2011	1,662.9	2.5	1,077.4	2,845.2	34.5	(2.5)	(2,294.2)
Ending Balance, shares at Mar. 31, 2011		249.1
Comprehensive income:
Net earnings	401.0			401.0
Foreign currency translation adjustment, net of tax (benefit) provision of $(2.6), $1.4 and $4.2 for 2012, 2011 and 2010, respectively	(0.5)				(0.5)
Unrealized gain on securities available for sale, net of tax (benefit) provision of $(0.2), $0.6 and $1.4 for 2012, 2011 and 2010, respectively	0.4					0.4
Treasury stock purchases	(818.7)						(818.7)
Shares issued/forfeited for share-based compensation	54.1		(44.5)	(0.9)			99.5
Share-based compensation expense	133.2		133.2
Tax benefit of share-based compensation expense	13.4		13.4
Ending Balance at Mar. 31, 2012	$ 1,445.8	$ 2.5	$ 1,179.5	$ 3,245.3	$ 34.0	$ (2.1)	$ (3,013.4)
Ending Balance, shares at Mar. 31, 2012		249.1