Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2015	Mar. 31, 2015
Statement of Financial Position [Abstract]
Accumulated depreciation	$ 846	$ 812
Preferred stock, No par value (in dollars per share)	$ 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 (in dollars per share)	$ 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	434,306,231	435,502,730
Treasury stock, Shares	155,388,850	154,192,351