Share-Based Compensation (Details Textual) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended	9 Months Ended
	Dec. 31, 2011	Dec. 31, 2011
Share-Based Compensation (Textual) [Abstract]
Total unrecognized compensation costs related to share-based awards	$ 237.5	$ 237.5
Weighted-average period (in years) to recognize total unrecognized compensation costs as expense		2
Time-based Nonvested Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested stock units granted	1.7	3.1
Weighted average grant fair value of nonvested stock units granted	$ 36.02	$ 43.58
Additional Share-Based Compensation (Textual) [Abstract]
Period over which nonvested stock units vest		one or three years
Market-based Nonvested Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested stock units granted	0.2	0.4
Weighted average grant fair value of nonvested stock units granted	$ 32.19	$ 42.23
Additional Share-Based Compensation (Textual) [Abstract]
Period over which nonvested stock units vest		50% increments over two- and three-year periods upon achievement of certain targets related to our relative shareholder return
Stock Options [Member]
Additional Share-Based Compensation (Textual) [Abstract]
Issuance of shares related to exercises of stock options and vesting of stock units	0.3	1.3
Restricted Stock Units [Member]
Additional Share-Based Compensation (Textual) [Abstract]
Issuance of shares related to exercises of stock options and vesting of stock units	0.7	2.2