Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) (USD $) In Millions, except Share data	Sep. 30, 2011	Mar. 31, 2011
ASSETS
Accumulated depreciation	$ 671	$ 632
STOCKHOLDERS' EQUITY
Preferred stock, no par value	$ 0	$ 0
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.10	$ 0.10
Common stock, shares authorized	1,100,000,000	1,100,000,000
Common stock, shares issued	589,695,081	589,695,081
Common stock, shares outstanding	489,413,910	502,299,607
Treasury stock, shares	100,281,171	87,395,474