Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Sep. 30, 2013	Mar. 31, 2013
Statement of Financial Position [Abstract]
Accumulated depreciation	$ 826	$ 786
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	446,646,793	448,149,131
Treasury stock, Shares	143,048,288	141,545,950