Stock-Based Compensation (Narrative) (Details) (USD $)	12 Months Ended			0 Months Ended	12 Months Ended								0 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012	Aug. 14, 2012 Stock Option [Member]	Mar. 31, 2014 Stock Option [Member]	Mar. 31, 2013 Stock Option [Member]	Mar. 31, 2012 Stock Option [Member]	Mar. 31, 2014 Option Grants after April 1, 2006 [Member]	Mar. 31, 2014 Option Grants before April 1, 2006 [Member]	Mar. 31, 2014 Employee Stock Purchase Plan [Member]	Mar. 31, 2013 Employee Stock Purchase Plan [Member]	Mar. 31, 2012 Employee Stock Purchase Plan [Member]	Apr. 01, 2014 Employee Stock Purchase Plan [Member]
Share Based Compensation [Line Items]
Increase in shares available for issuance, stock option plan				4,000,000
Shares authorized					11,700,000					5,500,000
Shares available for issuance					4,100,000					1,300,000
Annual vesting percentage								25.00%	25.00%
Terms of awards								maximum term of eight years	maximum term of ten years
Weighted-average grant date fair value of stock options granted					$ 32.41	$ 29.40	$ 22.78			$ 19.27	$ 16.73	$ 13.16
Total intrinsic value of stock options exercised	$ 47,000,000	$ 125,100,000	$ 56,900,000
Weighted-average remaining contractual term of stock options outstanding					4 years 6 months
Unrecognized compensation expense related to non-vested stock options					42,000,000
Weighted-average vesting period of non-vested stock options (in years)					1 year 8 months
ESPP shared issued					817,016	2,423,265	1,253,672			218,109	261,193	282,947	55,121
Annual gross earnings withheld, maximum										15.00%
Percentage of market price employees pay for Company stock in ESPP										85.00%
Employee aggregate annual purchase limit maximum - ESPP										$ 25,000
Employee Stock Purchase Plan, purchase price lock-in period	12 months